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Wyrażenia zapytań

  • Artykuł

Wyrażenia zapytań umożliwiają wykonywanie zapytań względem źródła danych i umieszczanie danych w żądanym formularzu. Wyrażenia zapytań zapewniają obsługę LINQ w języku F#.

Składnia

query { expression }

Uwagi

Wyrażenia zapytania są typem wyrażenia obliczeniowego podobnego do wyrażeń sekwencji. Tak jak określasz sekwencję, podając kod w wyrażeniu sekwencji, należy określić zestaw danych, podając kod w wyrażeniu zapytania. W wyrażeniu sekwencji słowo kluczowe identyfikuje dane, yield które mają być zwracane w ramach wynikowej sekwencji. W wyrażeniach select zapytania słowo kluczowe wykonuje tę samą funkcję. Oprócz słowa kluczowego select język F# obsługuje również wiele operatorów zapytań, które są podobne do części instrukcji SQL SELECT. Oto przykład prostego wyrażenia zapytania wraz z kodem, który łączy się ze źródłem Northwind OData.

// Use the OData type provider to create types that can be used to access the Northwind database.
// Add References to FSharp.Data.TypeProviders and System.Data.Services.Client
open Microsoft.FSharp.Data.TypeProviders

type Northwind = ODataService<"http://services.odata.org/Northwind/Northwind.svc">
let db = Northwind.GetDataContext()

// A query expression.
let query1 =
    query {
        for customer in db.Customers do
            select customer
    }

// Print results
query1
|> Seq.iter (fun customer -> printfn "Company: %s Contact: %s" customer.CompanyName customer.ContactName)

W poprzednim przykładzie kodu wyrażenie zapytania jest w nawiasach klamrowych. Znaczenie kodu w wyrażeniu to, zwracanie każdego klienta w tabeli Customers w bazie danych w wynikach zapytania. Wyrażenia zapytań zwracają typ, który implementuje IQueryable<T> wartości i IEnumerable<T>, a więc mogą być iterated przy użyciu modułu Seq, jak pokazano w przykładzie.

Każdy typ wyrażenia obliczeniowego jest tworzony na podstawie klasy konstruktora. Klasa konstruktora dla wyrażenia obliczeniowego zapytania to QueryBuilder. Aby uzyskać więcej informacji, zobacz Wyrażenia obliczeniowe i Klasa QueryBuilder.

Operatory zapytań

Operatory zapytań umożliwiają określenie szczegółów zapytania, takich jak umieszczenie kryteriów dla zwracanych rekordów lub określenie kolejności sortowania wyników. Źródło zapytania musi obsługiwać operator zapytania. Jeśli spróbujesz użyć nieobsługiwanego operatora zapytania, System.NotSupportedException zostanie zgłoszony.

Wyrażenia, które można przetłumaczyć na język SQL, są dozwolone w wyrażeniach zapytań. Na przykład żadne wywołania funkcji nie są dozwolone w wyrażeniach podczas korzystania z where operatora zapytania.

Tabela 1 zawiera dostępne operatory zapytań. Ponadto zobacz Tabela2, która porównuje zapytania SQL i równoważne wyrażenia zapytań języka F# w dalszej części tego tematu. Niektóre operatory zapytań nie są obsługiwane przez niektórych dostawców typów. W szczególności dostawca typu OData jest ograniczony do operatorów zapytań, które obsługuje z powodu ograniczeń w usłudze OData.

W tej tabeli założono, że baza danych ma następującą postać:

Diagram that shows a sample database.

Kod w poniższych tabelach zakłada również następujący kod połączenia z bazą danych. Projekty powinny dodawać odwołania do zestawów System.Data, System.Data.Linq i FSharp.Data.TypeProviders. Kod tworzący tę bazę danych znajduje się na końcu tego tematu.

open System
open Microsoft.FSharp.Data.TypeProviders
open System.Data.Linq.SqlClient
open System.Linq
open Microsoft.FSharp.Linq

type schema = SqlDataConnection< @"Data Source=SERVER\INSTANCE;Initial Catalog=MyDatabase;Integrated Security=SSPI;" >

let db = schema.GetDataContext()

// Needed for some query operator examples:
let data = [ 1; 5; 7; 11; 18; 21]

Tabela 1. Operatory zapytań

Operator opis
contains Określa, czy wybrane elementy zawierają określony element.

query {
    for student in db.Student do
    select student.Age.Value
    contains 11
}
countZwraca liczbę wybranych elementów.

query {
    for student in db.Student do
    select student
    count
}
lastWybiera ostatni element wybranych do tej pory.

query {
    for number in data do
    last
}
lastOrDefaultWybiera ostatni element wybranych do tej pory lub wartość domyślną, jeśli żaden element nie zostanie znaleziony.

query {
    for number in data do
    where (number < 0)
    lastOrDefault
}
exactlyOneWybiera wybrany do tej pory pojedynczy, określony element. Jeśli istnieje wiele elementów, zgłaszany jest wyjątek.

query {
    for student in db.Student do
    where (student.StudentID = 1)
    select student
    exactlyOne
}
exactlyOneOrDefaultWybiera pojedynczy, konkretny element wybranych do tej pory lub wartość domyślną, jeśli ten element nie zostanie znaleziony.

query {
    for student in db.Student do
    where (student.StudentID = 1)
    select student
    exactlyOneOrDefault
}
headOrDefaultWybiera pierwszy element wybranych do tej pory lub wartość domyślną, jeśli sekwencja nie zawiera żadnych elementów.

query {
    for student in db.Student do
    select student
    headOrDefault
}
selectProjektuje każdy z wybranych do tej pory elementów.

query {
    for student in db.Student do
    select student
}
whereWybiera elementy na podstawie określonego predykatu.

query {
    for student in db.Student do
    where (student.StudentID > 4)
    select student
}
minByWybiera wartość dla każdego wybranego elementu do tej pory i zwraca minimalną wynikową wartość.

query {
    for student in db.Student do
    minBy student.StudentID
}
maxByWybiera wartość dla każdego wybranego elementu do tej pory i zwraca maksymalną wartość wynikową.

query {
    for student in db.Student do
    maxBy student.StudentID
}
groupByGrupuje elementy wybrane do tej pory zgodnie z określonym selektorem kluczy.

query {
    for student in db.Student do
    groupBy student.Age into g
    select (g.Key, g.Count())
}
sortBySortuje elementy wybrane do tej pory w kolejności rosnącej według danego klucza sortowania.

query {
    for student in db.Student do
    sortBy student.Name
    select student
}
sortByDescendingSortuje elementy wybrane do tej pory w kolejności malejącej według danego klucza sortowania.

query {
    for student in db.Student do
    sortByDescending student.Name
    select student
}
thenByWykonuje kolejną kolejność elementów wybranych do tej pory w kolejności rosnącej przez dany klucz sortowania. Ten operator może być używany tylko po , sortBysortByDescending, thenBylub thenByDescending.

query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenBy student.Name
    select student
}
thenByDescendingWykonuje kolejną kolejność elementów wybranych do tej pory w kolejności malejącej według danego klucza sortowania. Ten operator może być używany tylko po , sortBysortByDescending, thenBylub thenByDescending.

query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenByDescending student.Name
    select student
}
groupValByWybiera wartość dla każdego elementu wybranego do tej pory i grupuje elementy według danego klucza.

query {
    for student in db.Student do
    groupValBy student.Name student.Age into g
    select (g, g.Key, g.Count())
}
joinKoreluje dwa zestawy wybranych wartości na podstawie pasujących kluczy. Należy pamiętać, że kolejność kluczy wokół znaku = zalogowanie wyrażenia sprzężenia jest znacząca. We wszystkich sprzężeniach, jeśli wiersz jest podzielony po symbolu -> , wcięcie musi być wcięcie co najmniej do słowa kluczowego for.

query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    select (student, selection)
}
groupJoinKoreluje dwa zestawy wybranych wartości na podstawie pasujących kluczy i grupuje wyniki. Należy pamiętać, że kolejność kluczy wokół znaku = zalogowanie wyrażenia sprzężenia jest znacząca.

query {
    for student in db.Student do
    groupJoin courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID) into g
    for courseSelection in g do
    join course in db.Course
        on (courseSelection.CourseID = course.CourseID)
    select (student.Name, course.CourseName)
}
leftOuterJoinKoreluje dwa zestawy wybranych wartości na podstawie pasujących kluczy i grupuje wyniki. Jeśli jakakolwiek grupa jest pusta, zamiast tego zostanie użyta grupa z pojedynczą wartością domyślną. Należy pamiętać, że kolejność kluczy wokół znaku = zalogowanie wyrażenia sprzężenia jest znacząca.

query {
    for student in db.Student do
    leftOuterJoin selection in db.CourseSelection
        on (student.StudentID = selection.StudentID) into result
    for selection in result.DefaultIfEmpty() do
    select (student, selection)
}
sumByNullableWybiera wartość dopuszczaną do wartości null dla każdego elementu wybranego do tej pory i zwraca sumę tych wartości. Jeśli jakiekolwiek dopuszczanie wartości null nie ma wartości, jest ignorowane.

query {
    for student in db.Student do
    sumByNullable student.Age
}
minByNullableWybiera wartość dopuszczaną do wartości null dla każdego elementu wybranego do tej pory i zwraca minimalną z tych wartości. Jeśli jakiekolwiek dopuszczanie wartości null nie ma wartości, jest ignorowane.

query {
    for student in db.Student do
    minByNullable student.Age
}
maxByNullableWybiera wartość dopuszczaną do wartości null dla każdego elementu wybranego do tej pory i zwraca maksymalną z tych wartości. Jeśli jakiekolwiek dopuszczanie wartości null nie ma wartości, jest ignorowane.

query {
    for student in db.Student do
    maxByNullable student.Age
}
averageByNullableWybiera wartość dopuszczaną do wartości null dla każdego elementu wybranego do tej pory i zwraca średnią tych wartości. Jeśli jakiekolwiek dopuszczanie wartości null nie ma wartości, jest ignorowane.

query {
    for student in db.Student do
    averageByNullable (Nullable.float student.Age)
}
averageByWybiera wartość dla każdego wybranego elementu do tej pory i zwraca średnią tych wartości.

query {
    for student in db.Student do
    averageBy (float student.StudentID)
}
distinctWybiera różne elementy z wybranych do tej pory elementów.

query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    distinct
}
existsOkreśla, czy dowolny wybrany element do tej pory spełnia warunek.

query {
    for student in db.Student do
    where
        (query {
            for courseSelection in db.CourseSelection do
            exists (courseSelection.StudentID = student.StudentID) })
    select student
}
findWybiera pierwszy wybrany do tej pory element, który spełnia określony warunek.

query {
    for student in db.Student do
    find (student.Name = "Abercrombie, Kim")
}
allOkreśla, czy wszystkie wybrane elementy do tej pory spełniają warunek.

query {
    for student in db.Student do
    all (SqlMethods.Like(student.Name, "%,%"))
}
headWybiera pierwszy element z wybranych do tej pory.

query {
    for student in db.Student do
    head
}
nthWybiera element w określonym indeksie spośród wybranych do tej pory.

query {
    for numbers in data do
    nth 3
}
skipPomija określoną liczbę wybranych do tej pory elementów, a następnie wybiera pozostałe elementy.

query {
    for student in db.Student do
    skip 1
}
skipWhilePomija elementy w sekwencji, o ile określony warunek jest spełniony, a następnie wybiera pozostałe elementy.

query {
    for number in data do
    skipWhile (number < 3)
    select student
}
sumByWybiera wartość dla każdego wybranego elementu do tej pory i zwraca sumę tych wartości.

query {
    for student in db.Student do
    sumBy student.StudentID
}
takeWybiera określoną liczbę ciągłych elementów z wybranych do tej pory.

query {
    for student in db.Student do
    select student
    take 2
}
takeWhileWybiera elementy z sekwencji, o ile określony warunek jest spełniony, a następnie pomija pozostałe elementy.

query {
    for number in data do
    takeWhile (number < 10)
}
sortByNullableSortuje elementy wybrane do tej pory w kolejności rosnącej według danego klucza sortowania dopuszczającego wartość null.

query {
    for student in db.Student do
    sortByNullable student.Age
    select student
}
sortByNullableDescendingSortuje elementy wybrane do tej pory w kolejności malejącej według danego klucza sortowania dopuszczającego wartość null.

query {
    for student in db.Student do
    sortByNullableDescending student.Age
    select student
}
thenByNullableWykonuje kolejną kolejność elementów wybranych do tej pory w kolejności rosnącej przez dany klucz sortowania dopuszczający wartość null. Ten operator może być używany tylko natychmiast po wariantach sortBy, , sortByDescendingthenBylub , lub thenByDescendingdopuszczanych do wartości null.

query {
    for student in db.Student do
    sortBy student.Name
    thenByNullable student.Age
    select student
}
thenByNullableDescendingWykonuje kolejną kolejność elementów wybranych do tej pory w kolejności malejącej według danego klucza sortowania dopuszczającego wartość null. Ten operator może być używany tylko natychmiast po wariantach sortBy, , sortByDescendingthenBylub , lub thenByDescendingdopuszczanych do wartości null.

query {
    for student in db.Student do
    sortBy student.Name
    thenByNullableDescending student.Age
    select student
}

Porównanie języka Transact-SQL z wyrażeniem zapytania F#

W poniższej tabeli przedstawiono niektóre typowe zapytania Języka Transact-SQL i ich odpowiedniki w języku F#. Kod w tej tabeli zakłada również, że ta sama baza danych co poprzednia tabela i ten sam kod początkowy do skonfigurowania dostawcy typów.

Tabela 2. Transact-SQL i wyrażenia zapytania F#

Transact-SQL (nie uwzględnia wielkości liter) Wyrażenie zapytania języka F# (z uwzględnieniem wielkości liter)
Zaznacz wszystkie pola z tabeli.
SELECT * FROM Student

// All students.
query {
    for student in db.Student do
    select student
}
Zlicz rekordy w tabeli.
SELECT COUNT( * ) FROM Student

// Count of students.
query {
    for student in db.Student do
    count
}
EXISTS 
SELECT * FROM Student
WHERE EXISTS
  (SELECT * FROM CourseSelection
   WHERE CourseSelection.StudentID = Student.StudentID)

// Find students who have signed up at least one course.
query {
    for student in db.Student do
    where
        (query {
            for courseSelection in db.CourseSelection do
            exists (courseSelection.StudentID = student.StudentID) })
    select student
}
Grupowanie
SELECT Student.Age, COUNT( * ) FROM Student
GROUP BY Student.Age

// Group by age and count.
query {
    for n in db.Student do
    groupBy n.Age into g
    select (g.Key, g.Count())
}
// OR
query {
    for n in db.Student do
    groupValBy n.Age n.Age into g
    select (g.Key, g.Count())
}
Grupowanie z warunkiem.
SELECT Student.Age, COUNT( * )
FROM Student
GROUP BY Student.Age
HAVING student.Age > 10

// Group students by age where age > 10.
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Key.HasValue && g.Key.Value > 10)
    select (g.Key, g.Count())
}
Grupowanie z warunkiem liczby.
SELECT Student.Age, COUNT( * )
FROM Student
GROUP BY Student.Age
HAVING COUNT( * ) > 1

// Group students by age and count number of students
// at each age with more than 1 student.
query {
    for student in db.Student do
    groupBy student.Age into group
    where (group.Count() > 1)
    select (group.Key, group.Count())
}
Grupowanie, liczenie i sumowanie.
SELECT Student.Age, COUNT( * ), SUM(Student.Age) as total
FROM Student
GROUP BY Student.Age

// Group students by age and sum ages.
query {
    for student in db.Student do
    groupBy student.Age into g
    let total =
        query {
            for student in g do
            sumByNullable student.Age
        }
    select (g.Key, g.Count(), total)
}
Grupowanie, liczenie i porządkowanie według liczby.
SELECT Student.Age, COUNT( * ) as myCount
FROM Student
GROUP BY Student.Age
HAVING COUNT( * ) > 1
ORDER BY COUNT( * ) DESC

// Group students by age, count number of students
// at each age, and display all with count > 1
// in descending order of count.
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Count() > 1)
    sortByDescending (g.Count())
    select (g.Key, g.Count())
}
IN zestaw określonych wartości
SELECT *
FROM Student
WHERE Student.StudentID IN (1, 2, 5, 10)

// Select students where studentID is one of a given list.
let idQuery =
    query {
        for id in [1; 2; 5; 10] do
        select id
    }
query {
    for student in db.Student do
    where (idQuery.Contains(student.StudentID))
    select student
}
LIKE i TOP.
-- '_e%' matches strings where the second character is 'e'
SELECT TOP 2 * FROM Student
WHERE Student.Name LIKE '_e%'

// Look for students with Name match _e% pattern and take first two.
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "_e%") )
    select student
    take 2
}
LIKE z zestawem dopasowania wzorca.
-- '[abc]%' matches strings where the first character is
-- 'a', 'b', 'c', 'A', 'B', or 'C'
SELECT * FROM Student
WHERE Student.Name LIKE '[abc]%'

query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[abc]%") )
    select student
}
LIKE z ustawionym wzorcem wykluczeń.
-- '[^abc]%' matches strings where the first character is
-- not 'a', 'b', 'c', 'A', 'B', or 'C'
SELECT * FROM Student
WHERE Student.Name LIKE '[^abc]%'

// Look for students with name matching [^abc]%% pattern.
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[^abc]%") )
    select student
}
LIKE w jednym polu, ale wybierz inne pole.
SELECT StudentID AS ID FROM Student
WHERE Student.Name LIKE '[^abc]%'

query {
    for n in db.Student do
    where (SqlMethods.Like( n.Name, "[^abc]%") )
    select n.StudentID
}
LIKEz wyszukiwaniem podciągów.
SELECT * FROM Student
WHERE Student.Name like '%A%'

// Using Contains as a query filter.
query {
    for student in db.Student do
    where (student.Name.Contains("a"))
    select student
}
Proste JOIN z dwiema tabelami.
SELECT * FROM Student
JOIN CourseSelection
ON Student.StudentID = CourseSelection.StudentID

// Join Student and CourseSelection tables.
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    select (student, selection)
}
LEFT JOIN z dwiema tabelami.
SELECT * FROM Student
LEFT JOIN CourseSelection
ON Student.StudentID = CourseSelection.StudentID

//Left Join Student and CourseSelection tables.
query {
    for student in db.Student do
    leftOuterJoin selection in db.CourseSelection
        on (student.StudentID = selection.StudentID) into result
    for selection in result.DefaultIfEmpty() do
    select (student, selection)
}
JOIN Z COUNT
SELECT COUNT( * ) FROM Student
JOIN CourseSelection
ON Student.StudentID = CourseSelection.StudentID

// Join with count.
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    count
}
DISTINCT
SELECT DISTINCT StudentID FROM CourseSelection

// Join with distinct.
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    distinct
}
Zliczenie.
SELECT DISTINCT COUNT(StudentID) FROM CourseSelection

// Join with distinct and count.
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    distinct
    count
}
BETWEEN
SELECT * FROM Student
WHERE Student.Age BETWEEN 10 AND 15

// Selecting students with ages between 10 and 15.
query {
    for student in db.Student do
    where (student.Age ?>= 10 && student.Age ?< 15)
    select student
}
OR
SELECT * FROM Student
WHERE Student.Age = 11 OR Student.Age = 12

// Selecting students with age that's either 11 or 12.
query {
    for student in db.Student do
    where (student.Age.Value = 11 &#124;&#124; student.Age.Value = 12)
    select student
}
OR z kolejnością
SELECT * FROM Student
WHERE Student.Age = 12 OR Student.Age = 13
ORDER BY Student.Age DESC

// Selecting students in a certain age range and sorting.
query {
    for n in db.Student do
    where (n.Age.Value = 12 &#124;&#124; n.Age.Value = 13)
    sortByNullableDescending n.Age
    select n
}
TOP, ORi porządkowanie.
SELECT TOP 2 student.Name FROM Student
WHERE Student.Age = 11 OR Student.Age = 12
ORDER BY Student.Name DESC

// Selecting students with certain ages,
// taking account of the possibility of nulls.
query {
    for student in db.Student do
    where
        ((student.Age.HasValue && student.Age.Value = 11) &#124;&#124;
         (student.Age.HasValue && student.Age.Value = 12))
    sortByDescending student.Name
    select student.Name
    take 2
}
UNION z dwóch zapytań.
SELECT * FROM Student
UNION
SELECT * FROM lastStudent

let query1 =
    query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

let query2 =
    query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

query2.Union (query1)
Przecięcie dwóch zapytań.
SELECT * FROM Student
INTERSECT
SELECT * FROM LastStudent

let query1 =
    query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

let query2 =
    query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

query1.Intersect(query2)
CASE Warunek.
SELECT student.StudentID,
CASE Student.Age
  WHEN -1 THEN 100
  ELSE Student.Age
END,
Student.Age
FROM Student

// Using if statement to alter results for special value.
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
             (student.StudentID, System.Nullable<int>(100), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
Wiele przypadków.
SELECT Student.StudentID,
CASE Student.Age
  WHEN -1 THEN 100
  WHEN 0 THEN 1000
  ELSE Student.Age
END,
Student.Age
FROM Student

// Using if statement to alter results for special values.
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
             (student.StudentID, System.Nullable<int>(100), student.Age)
         elif student.Age.HasValue && student.Age.Value = 0 then
             (student.StudentID, System.Nullable<int>(1000), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
Wiele tabel.
SELECT * FROM Student, Course

// Multiple table select.
query {
    for student in db.Student do
    for course in db.Course do
    select (student, course)
}
Wiele sprzężeń.
SELECT Student.Name, Course.CourseName
FROM Student
JOIN CourseSelection
ON CourseSelection.StudentID = Student.StudentID
JOIN Course
ON Course.CourseID = CourseSelection.CourseID

// Multiple joins.
query {
    for student in db.Student do
    join courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID)
    join course in db.Course
        on (courseSelection.CourseID = course.CourseID)
    select (student.Name, course.CourseName)
}
Wiele lewych sprzężeń zewnętrznych.
SELECT Student.Name, Course.CourseName
FROM Student
LEFT OUTER JOIN CourseSelection
ON CourseSelection.StudentID = Student.StudentID
LEFT OUTER JOIN Course
ON Course.CourseID = CourseSelection.CourseID

// Using leftOuterJoin with multiple joins.
query {
    for student in db.Student do
    leftOuterJoin courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID) into g1
    for courseSelection in g1.DefaultIfEmpty() do
    leftOuterJoin course in db.Course
        on (courseSelection.CourseID = course.CourseID) into g2
    for course in g2.DefaultIfEmpty() do
    select (student.Name, course.CourseName)
}

Poniższy kod może służyć do utworzenia przykładowej bazy danych dla tych przykładów.

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

USE [master];
GO

IF EXISTS (SELECT * FROM sys.databases WHERE name = 'MyDatabase')
DROP DATABASE MyDatabase;
GO

-- Create the MyDatabase database.
CREATE DATABASE MyDatabase COLLATE SQL_Latin1_General_CP1_CI_AS;
GO

-- Specify a simple recovery model
-- to keep the log growth to a minimum.
ALTER DATABASE MyDatabase
SET RECOVERY SIMPLE;
GO

USE MyDatabase;
GO

CREATE TABLE [dbo].[Course] (
[CourseID]   INT           NOT NULL,
[CourseName] NVARCHAR (50) NOT NULL,
PRIMARY KEY CLUSTERED ([CourseID] ASC)
);

CREATE TABLE [dbo].[Student] (
[StudentID] INT           NOT NULL,
[Name]      NVARCHAR (50) NOT NULL,
[Age]       INT           NULL,
PRIMARY KEY CLUSTERED ([StudentID] ASC)
);

CREATE TABLE [dbo].[CourseSelection] (
[ID]        INT NOT NULL,
[StudentID] INT NOT NULL,
[CourseID]  INT NOT NULL,
PRIMARY KEY CLUSTERED ([ID] ASC),
CONSTRAINT [FK_CourseSelection_ToTable] FOREIGN KEY ([StudentID]) REFERENCES [dbo].[Student] ([StudentID]) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT [FK_CourseSelection_Course_1] FOREIGN KEY ([CourseID]) REFERENCES [dbo].[Course] ([CourseID]) ON DELETE NO ACTION ON UPDATE NO ACTION
);

CREATE TABLE [dbo].[LastStudent] (
[StudentID] INT           NOT NULL,
[Name]      NVARCHAR (50) NOT NULL,
[Age]       INT           NULL,
PRIMARY KEY CLUSTERED ([StudentID] ASC)
);

-- Insert data into the tables.
USE MyDatabase
INSERT INTO Course (CourseID, CourseName)
VALUES(1, 'Algebra I');
INSERT INTO Course (CourseID, CourseName)
VALUES(2, 'Trigonometry');
INSERT INTO Course (CourseID, CourseName)
VALUES(3, 'Algebra II');
INSERT INTO Course (CourseID, CourseName)
VALUES(4, 'History');
INSERT INTO Course (CourseID, CourseName)
VALUES(5, 'English');
INSERT INTO Course (CourseID, CourseName)
VALUES(6, 'French');
INSERT INTO Course (CourseID, CourseName)
VALUES(7, 'Chinese');

INSERT INTO Student (StudentID, Name, Age)
VALUES(1, 'Abercrombie, Kim', 10);
INSERT INTO Student (StudentID, Name, Age)
VALUES(2, 'Abolrous, Hazen', 14);
INSERT INTO Student (StudentID, Name, Age)
VALUES(3, 'Hance, Jim', 12);
INSERT INTO Student (StudentID, Name, Age)
VALUES(4, 'Adams, Terry', 12);
INSERT INTO Student (StudentID, Name, Age)
VALUES(5, 'Hansen, Claus', 11);
INSERT INTO Student (StudentID, Name, Age)
VALUES(6, 'Penor, Lori', 13);
INSERT INTO Student (StudentID, Name, Age)
VALUES(7, 'Perham, Tom', 12);
INSERT INTO Student (StudentID, Name, Age)
VALUES(8, 'Peng, Yun-Feng', NULL);

INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(1, 1, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(2, 1, 3);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(3, 1, 5);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(4, 2, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(5, 2, 5);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(6, 2, 6);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(7, 2, 3);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(8, 3, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(9, 3, 1);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(10, 4, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(11, 4, 5);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(12, 4, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(13, 5, 3);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(14, 5, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(15, 7, 3);

Poniższy kod zawiera przykładowy kod, który zostanie wyświetlony w tym temacie.

#if INTERACTIVE
#r "FSharp.Data.TypeProviders.dll"
#r "System.Data.dll"
#r "System.Data.Linq.dll"
#endif
open System
open Microsoft.FSharp.Data.TypeProviders
open System.Data.Linq.SqlClient
open System.Linq

type schema = SqlDataConnection<"Data Source=SERVER\INSTANCE;Initial Catalog=MyDatabase;Integrated Security=SSPI;">

let db = schema.GetDataContext()

let data = [1; 5; 7; 11; 18; 21]

type Nullable<'T when 'T : ( new : unit -> 'T) and 'T : struct and 'T :> ValueType > with
    member this.Print() =
        if this.HasValue then this.Value.ToString()
        else "NULL"

printfn "\ncontains query operator"
query {
    for student in db.Student do
    select student.Age.Value
    contains 11
}
|> printfn "Is at least one student age 11? %b"

printfn "\ncount query operator"
query {
    for student in db.Student do
    select student
    count
}
|> printfn "Number of students: %d"

printfn "\nlast query operator."
let num =
    query {
        for number in data do
        sortBy number
        last
    }
printfn "Last number: %d" num

open Microsoft.FSharp.Linq

printfn "\nlastOrDefault query operator."
query {
    for number in data do
    sortBy number
    lastOrDefault
}
|> printfn "lastOrDefault: %d"

printfn "\nexactlyOne query operator."
let student2 =
    query {
        for student in db.Student do
        where (student.StudentID = 1)
        select student
        exactlyOne
    }
printfn "Student with StudentID = 1 is %s" student2.Name

printfn "\nexactlyOneOrDefault query operator."
let student3 =
    query {
        for student in db.Student do
        where (student.StudentID = 1)
        select student
        exactlyOneOrDefault
    }
printfn "Student with StudentID = 1 is %s" student3.Name

printfn "\nheadOrDefault query operator."
let student4 =
    query {
        for student in db.Student do
        select student
        headOrDefault
    }
printfn "head student is %s" student4.Name

printfn "\nselect query operator."
query {
    for student in db.Student do
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nwhere query operator."
query {
    for student in db.Student do
    where (student.StudentID > 4)
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nminBy query operator."
let student5 =
    query {
        for student in db.Student do
        minBy student.StudentID
    }

printfn "\nmaxBy query operator."
let student6 =
    query {
        for student in db.Student do
        maxBy student.StudentID
    }

printfn "\ngroupBy query operator."
query {
    for student in db.Student do
    groupBy student.Age into g
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, count) -> printfn "Age: %s Count at that age: %d" (age.Print()) count)

printfn "\nsortBy query operator."
query {
    for student in db.Student do
    sortBy student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nsortByDescending query operator."
query {
    for student in db.Student do
    sortByDescending student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nthenBy query operator."
query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenBy student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.Age.Value student.Name)

printfn "\nthenByDescending query operator."
query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenByDescending student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.Age.Value student.Name)

printfn "\ngroupValBy query operator."
query {
    for student in db.Student do
    groupValBy student.Name student.Age into g
    select (g, g.Key, g.Count())
}
|> Seq.iter (fun (group, age, count) ->
    printfn "Age: %s Count at that age: %d" (age.Print()) count
    group |> Seq.iter (fun name -> printfn "Name: %s" name))

printfn "\n sumByNullable query operator"
query {
    for student in db.Student do
    sumByNullable student.Age
}
|> (fun sum -> printfn "Sum of ages: %s" (sum.Print()))

printfn "\n minByNullable"
query {
    for student in db.Student do
    minByNullable student.Age
}
|> (fun age -> printfn "Minimum age: %s" (age.Print()))

printfn "\n maxByNullable"
query {
    for student in db.Student do
    maxByNullable student.Age
}
|> (fun age -> printfn "Maximum age: %s" (age.Print()))

printfn "\n averageBy"
query {
    for student in db.Student do
    averageBy (float student.StudentID)
}
|> printfn "Average student ID: %f"

printfn "\n averageByNullable"
query {
    for student in db.Student do
    averageByNullable (Nullable.float student.Age)
}
|> (fun avg -> printfn "Average age: %s" (avg.Print()))

printfn "\n find query operator"
query {
    for student in db.Student do
    find (student.Name = "Abercrombie, Kim")
}
|> (fun student -> printfn "Found a match with StudentID = %d" student.StudentID)

printfn "\n all query operator"
query {
    for student in db.Student do
    all (SqlMethods.Like(student.Name, "%,%"))
}
|> printfn "Do all students have a comma in the name? %b"

printfn "\n head query operator"
query {
    for student in db.Student do
    head
}
|> (fun student -> printfn "Found the head student with StudentID = %d" student.StudentID)

printfn "\n nth query operator"
query {
    for numbers in data do
    nth 3
}
|> printfn "Third number is %d"

printfn "\n skip query operator"
query {
    for student in db.Student do
    skip 1
}
|> Seq.iter (fun student -> printfn "StudentID = %d" student.StudentID)

printfn "\n skipWhile query operator"
query {
    for number in data do
    skipWhile (number < 3)
    select number
}
|> Seq.iter (fun number -> printfn "Number = %d" number)

printfn "\n sumBy query operator"
query {
    for student in db.Student do
    sumBy student.StudentID
}
|> printfn "Sum of student IDs: %d"

printfn "\n take query operator"
query {
    for student in db.Student do
    select student
    take 2
}
|> Seq.iter (fun student -> printfn "StudentID = %d" student.StudentID)

printfn "\n takeWhile query operator"
query {
    for number in data do
    takeWhile (number < 10)
}
|> Seq.iter (fun number -> printfn "Number = %d" number)

printfn "\n sortByNullable query operator"
query {
    for student in db.Student do
    sortByNullable student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "\n sortByNullableDescending query operator"
query {
    for student in db.Student do
    sortByNullableDescending student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "\n thenByNullable query operator"
query {
    for student in db.Student do
    sortBy student.Name
    thenByNullable student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "\n thenByNullableDescending query operator"
query {
    for student in db.Student do
    sortBy student.Name
    thenByNullableDescending student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "All students: "
query {
    for student in db.Student do
    select student
}
|> Seq.iter (fun student -> printfn "%s %d %s" student.Name student.StudentID (student.Age.Print()))

printfn "\nCount of students: "
query {
    for student in db.Student do
    count
}
|> (fun count -> printfn "Student count: %d" count)

printfn "\nExists."
query {
    for student in db.Student do
    where
        (query {
            for courseSelection in db.CourseSelection do
            exists (courseSelection.StudentID = student.StudentID) })
    select student
}
|> Seq.iter (fun student -> printfn "%A" student.Name)

printfn "\n Group by age and count"
query {
    for n in db.Student do
    groupBy n.Age into g
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, count) -> printfn "%s %d" (age.Print()) count)

printfn "\n Group value by age."
query {
    for n in db.Student do
    groupValBy n.Age n.Age into g
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, count) -> printfn "%s %d" (age.Print()) count)

printfn "\nGroup students by age where age > 10."
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Key.HasValue && g.Key.Value > 10)
    select (g, g.Key)
}
|> Seq.iter (fun (students, age) ->
    printfn "Age: %s" (age.Value.ToString())
    students
    |> Seq.iter (fun student -> printfn "%s" student.Name))

printfn "\nGroup students by age and print counts of number of students at each age with more than 1 student."
query {
    for student in db.Student do
    groupBy student.Age into group
    where (group.Count() > 1)
    select (group.Key, group.Count())
}
|> Seq.iter (fun (age, ageCount) ->
    printfn "Age: %s Count: %d" (age.Print()) ageCount)

printfn "\nGroup students by age and sum ages."
query {
    for student in db.Student do
    groupBy student.Age into g
    let total = query { for student in g do sumByNullable student.Age }
    select (g.Key, g.Count(), total)
}
|> Seq.iter (fun (age, count, total) ->
    printfn "Age: %d" (age.GetValueOrDefault())
    printfn "Count: %d" count
    printfn "Total years: %s" (total.ToString()))

printfn "\nGroup students by age and count number of students at each age, and display all with count > 1 in descending order of count."
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Count() > 1)
    sortByDescending (g.Count())
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, myCount) ->
    printfn "Age: %s" (age.Print())
    printfn "Count: %d" myCount)

printfn "\n Select students from a set of IDs"
let idList = [1; 2; 5; 10]
let idQuery =
    query { for id in idList do select id }
query {
    for student in db.Student do
    where (idQuery.Contains(student.StudentID))
    select student
}
|> Seq.iter (fun student ->
    printfn "Name: %s" student.Name)

printfn "\nLook for students with Name match _e%% pattern and take first two."
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "_e%") )
    select student
    take 2
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nLook for students with Name matching [abc]%% pattern."
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[abc]%") )
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nLook for students with name matching [^abc]%% pattern."
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[^abc]%") )
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nLook for students with name matching [^abc]%% pattern and select ID."
query {
    for n in db.Student do
    where (SqlMethods.Like( n.Name, "[^abc]%") )
    select n.StudentID
}
|> Seq.iter (fun id -> printfn "%d" id)

printfn "\n Using Contains as a query filter."
query {
    for student in db.Student do
    where (student.Name.Contains("a"))
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nSearching for names from a list."
let names = [|"a";"b";"c"|]
query {
    for student in db.Student do
    if names.Contains (student.Name) then select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nJoin Student and CourseSelection tables."
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    select (student, selection)
}
|> Seq.iter (fun (student, selection) -> printfn "%d %s %d" student.StudentID student.Name selection.CourseID)

printfn "\nLeft Join Student and CourseSelection tables."
query {
    for student in db.Student do
    leftOuterJoin selection in db.CourseSelection
        on (student.StudentID = selection.StudentID) into result
    for selection in result.DefaultIfEmpty() do
    select (student, selection)
}
|> Seq.iter (fun (student, selection) ->
    let selectionID, studentID, courseID =
        match selection with
        | null -> "NULL", "NULL", "NULL"
        | sel -> (sel.ID.ToString(), sel.StudentID.ToString(), sel.CourseID.ToString())
    printfn "%d %s %d %s %s %s" student.StudentID student.Name (student.Age.GetValueOrDefault()) selectionID studentID courseID)

printfn "\nJoin with count"
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    count
}
|> printfn "%d"

printfn "\n Join with distinct."
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    distinct
}
|> Seq.iter (fun (student, selection) -> printfn "%s %d" student.Name selection.CourseID)

printfn "\n Join with distinct and count."
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    distinct
    count
}
|> printfn "%d"

printfn "\n Selecting students with age between 10 and 15."
query {
    for student in db.Student do
    where (student.Age.Value >= 10 && student.Age.Value < 15)
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\n Selecting students with age either 11 or 12."
query {
    for student in db.Student do
    where (student.Age.Value = 11 || student.Age.Value = 12)
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\n Selecting students in a certain age range and sorting."
query {
    for n in db.Student do
    where (n.Age.Value = 12 || n.Age.Value = 13)
    sortByNullableDescending n.Age
    select n
}
|> Seq.iter (fun student -> printfn "%s %s" student.Name (student.Age.Print()))

printfn "\n Selecting students with certain ages, taking account of possibility of nulls."
query {
    for student in db.Student do
    where
        ((student.Age.HasValue && student.Age.Value = 11) ||
         (student.Age.HasValue && student.Age.Value = 12))
    sortByDescending student.Name
    select student.Name
    take 2
}
|> Seq.iter (fun name -> printfn "%s" name)

printfn "\n Union of two queries."
module Queries =
    let query1 = query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

    let query2 = query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

    query2.Union (query1)
    |> Seq.iter (fun (name, age) -> printfn "%s %s" name (age.Print()))

printfn "\n Intersect of two queries."
module Queries2 =
    let query1 = query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

    let query2 = query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

    query1.Intersect(query2)
    |> Seq.iter (fun (name, age) -> printfn "%s %s" name (age.Print()))

printfn "\n Using if statement to alter results for special value."
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
            (student.StudentID, System.Nullable<int>(100), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
|> Seq.iter (fun (id, value, age) -> printfn "%d %s %s" id (value.Print()) (age.Print()))

printfn "\n Using if statement to alter results special values."
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
            (student.StudentID, System.Nullable<int>(100), student.Age)
         elif student.Age.HasValue && student.Age.Value = 0 then
            (student.StudentID, System.Nullable<int>(100), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
|> Seq.iter (fun (id, value, age) -> printfn "%d %s %s" id (value.Print()) (age.Print()))

printfn "\n Multiple table select."
query {
    for student in db.Student do
    for course in db.Course do
    select (student, course)
}
|> Seq.iteri (fun index (student, course) ->
    if index = 0 then
        printfn "StudentID Name Age CourseID CourseName"
    printfn "%d %s %s %d %s" student.StudentID student.Name (student.Age.Print()) course.CourseID course.CourseName)

printfn "\nMultiple Joins"
query {
    for student in db.Student do
    join courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID)
    join course in db.Course
        on (courseSelection.CourseID = course.CourseID)
    select (student.Name, course.CourseName)
}
|> Seq.iter (fun (studentName, courseName) -> printfn "%s %s" studentName courseName)

printfn "\nMultiple Left Outer Joins"
query {
    for student in db.Student do
    leftOuterJoin courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID) into g1
    for courseSelection in g1.DefaultIfEmpty() do
    leftOuterJoin course in db.Course
        on (courseSelection.CourseID = course.CourseID) into g2
    for course in g2.DefaultIfEmpty() do
    select (student.Name, course.CourseName)
}
|> Seq.iter (fun (studentName, courseName) -> printfn "%s %s" studentName courseName)

Oto pełne dane wyjściowe, gdy ten kod jest uruchamiany w języku F# Interactive.

--> Referenced 'C:\Program Files (x86)\Reference Assemblies\Microsoft\FSharp\3.0\Runtime\v4.0\Type Providers\FSharp.Data.TypeProviders.dll'

--> Referenced 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Data.dll'

--> Referenced 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Data.Linq.dll'

contains query operator
Binding session to 'C:\Users\ghogen\AppData\Local\Temp\tmp5E3C.dll'...
Binding session to 'C:\Users\ghogen\AppData\Local\Temp\tmp611A.dll'...
Is at least one student age 11? true

count query operator
Number of students: 8

last query operator.
Last number: 21

lastOrDefault query operator.
lastOrDefault: 21

exactlyOne query operator.
Student with StudentID = 1 is Abercrombie, Kim

exactlyOneOrDefault query operator.
Student with StudentID = 1 is Abercrombie, Kim

headOrDefault query operator.
head student is Abercrombie, Kim

select query operator.
StudentID, Name: 1 Abercrombie, Kim
StudentID, Name: 2 Abolrous, Hazen
StudentID, Name: 3 Hance, Jim
StudentID, Name: 4 Adams, Terry
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 6 Penor, Lori
StudentID, Name: 7 Perham, Tom
StudentID, Name: 8 Peng, Yun-Feng

where query operator.
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 6 Penor, Lori
StudentID, Name: 7 Perham, Tom
StudentID, Name: 8 Peng, Yun-Feng

minBy query operator.

maxBy query operator.

groupBy query operator.
Age: NULL Count at that age: 1
Age: 10 Count at that age: 1
Age: 11 Count at that age: 1
Age: 12 Count at that age: 3
Age: 13 Count at that age: 1
Age: 14 Count at that age: 1

sortBy query operator.
StudentID, Name: 1 Abercrombie, Kim
StudentID, Name: 2 Abolrous, Hazen
StudentID, Name: 4 Adams, Terry
StudentID, Name: 3 Hance, Jim
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 8 Peng, Yun-Feng
StudentID, Name: 6 Penor, Lori
StudentID, Name: 7 Perham, Tom

sortByDescending query operator.
StudentID, Name: 7 Perham, Tom
StudentID, Name: 6 Penor, Lori
StudentID, Name: 8 Peng, Yun-Feng
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 3 Hance, Jim
StudentID, Name: 4 Adams, Terry
StudentID, Name: 2 Abolrous, Hazen
StudentID, Name: 1 Abercrombie, Kim

thenBy query operator.
StudentID, Name: 10 Abercrombie, Kim
StudentID, Name: 11 Hansen, Claus
StudentID, Name: 12 Adams, Terry
StudentID, Name: 12 Hance, Jim
StudentID, Name: 12 Perham, Tom
StudentID, Name: 13 Penor, Lori
StudentID, Name: 14 Abolrous, Hazen

thenByDescending query operator.
StudentID, Name: 10 Abercrombie, Kim
StudentID, Name: 11 Hansen, Claus
StudentID, Name: 12 Perham, Tom
StudentID, Name: 12 Hance, Jim
StudentID, Name: 12 Adams, Terry
StudentID, Name: 13 Penor, Lori
StudentID, Name: 14 Abolrous, Hazen

groupValBy query operator.
Age: NULL Count at that age: 1
Name: Peng, Yun-Feng
Age: 10 Count at that age: 1
Name: Abercrombie, Kim
Age: 11 Count at that age: 1
Name: Hansen, Claus
Age: 12 Count at that age: 3
Name: Hance, Jim
Name: Adams, Terry
Name: Perham, Tom
Age: 13 Count at that age: 1
Name: Penor, Lori
Age: 14 Count at that age: 1
Name: Abolrous, Hazen

sumByNullable query operator
Sum of ages: 84

minByNullable
Minimum age: 10

maxByNullable
Maximum age: 14

averageBy
Average student ID: 4.500000

averageByNullable
Average age: 12

find query operator
Found a match with StudentID = 1

all query operator
Do all students have a comma in the name? true

head query operator
Found the head student with StudentID = 1

nth query operator
Third number is 11

skip query operator
StudentID = 2
StudentID = 3
StudentID = 4
StudentID = 5
StudentID = 6
StudentID = 7
StudentID = 8

skipWhile query operator
Number = 5
Number = 7
Number = 11
Number = 18
Number = 21

sumBy query operator
Sum of student IDs: 36

take query operator
StudentID = 1
StudentID = 2

takeWhile query operator
Number = 1
Number = 5
Number = 7

sortByNullable query operator
StudentID, Name, Age: 8 Peng, Yun-Feng NULL
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 7 Perham, Tom 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 2 Abolrous, Hazen 14

sortByNullableDescending query operator
StudentID, Name, Age: 2 Abolrous, Hazen 14
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 7 Perham, Tom 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 8 Peng, Yun-Feng NULL

thenByNullable query operator
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 2 Abolrous, Hazen 14
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 8 Peng, Yun-Feng NULL
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 7 Perham, Tom 12

thenByNullableDescending query operator
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 2 Abolrous, Hazen 14
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 8 Peng, Yun-Feng NULL
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 7 Perham, Tom 12
All students:
Abercrombie, Kim 1 10
Abolrous, Hazen 2 14
Hance, Jim 3 12
Adams, Terry 4 12
Hansen, Claus 5 11
Penor, Lori 6 13
Perham, Tom 7 12
Peng, Yun-Feng 8 NULL

Count of students:
Student count: 8

Exists.
"Abercrombie, Kim"
"Abolrous, Hazen"
"Hance, Jim"
"Adams, Terry"
"Hansen, Claus"
"Perham, Tom"

Group by age and count
NULL 1
10 1
11 1
12 3
13 1
14 1

Group value by age.
NULL 1
10 1
11 1
12 3
13 1
14 1

Group students by age where age > 10.
Age: 11
Hansen, Claus
Age: 12
Hance, Jim
Adams, Terry
Perham, Tom
Age: 13
Penor, Lori
Age: 14
Abolrous, Hazen

Group students by age and print counts of number of students at each age with more than 1 student.
Age: 12 Count: 3

Group students by age and sum ages.
Age: 0
Count: 1
Total years:
Age: 10
Count: 1
Total years: 10
Age: 11
Count: 1
Total years: 11
Age: 12
Count: 3
Total years: 36
Age: 13
Count: 1
Total years: 13
Age: 14
Count: 1
Total years: 14

Group students by age and count number of students at each age, and display all with count > 1 in descending order of count.
Age: 12
Count: 3

Select students from a set of IDs
Name: Abercrombie, Kim
Name: Abolrous, Hazen
Name: Hansen, Claus

Look for students with Name match _e% pattern and take first two.
Penor, Lori
Perham, Tom

Look for students with Name matching [abc]% pattern.
Abercrombie, Kim
Abolrous, Hazen
Adams, Terry

Look for students with name matching [^abc]% pattern.
Hance, Jim
Hansen, Claus
Penor, Lori
Perham, Tom
Peng, Yun-Feng

Look for students with name matching [^abc]% pattern and select ID.
3
5
6
7
8

Using Contains as a query filter.
Abercrombie, Kim
Abolrous, Hazen
Hance, Jim
Adams, Terry
Hansen, Claus
Perham, Tom

Searching for names from a list.

Join Student and CourseSelection tables.
2 Abolrous, Hazen 2
3 Hance, Jim 3
5 Hansen, Claus 5
2 Abolrous, Hazen 2
5 Hansen, Claus 5
6 Penor, Lori 6
3 Hance, Jim 3
2 Abolrous, Hazen 2
1 Abercrombie, Kim 1
2 Abolrous, Hazen 2
5 Hansen, Claus 5
2 Abolrous, Hazen 2
3 Hance, Jim 3
2 Abolrous, Hazen 2
3 Hance, Jim 3

Left Join Student and CourseSelection tables.
1 Abercrombie, Kim 10 9 3 1
2 Abolrous, Hazen 14 1 1 2
2 Abolrous, Hazen 14 4 2 2
2 Abolrous, Hazen 14 8 3 2
2 Abolrous, Hazen 14 10 4 2
2 Abolrous, Hazen 14 12 4 2
2 Abolrous, Hazen 14 14 5 2
3 Hance, Jim 12 2 1 3
3 Hance, Jim 12 7 2 3
3 Hance, Jim 12 13 5 3
3 Hance, Jim 12 15 7 3
4 Adams, Terry 12 NULL NULL NULL
5 Hansen, Claus 11 3 1 5
5 Hansen, Claus 11 5 2 5
5 Hansen, Claus 11 11 4 5
6 Penor, Lori 13 6 2 6
7 Perham, Tom 12 NULL NULL NULL
8 Peng, Yun-Feng 0 NULL NULL NULL

Join with count
15

Join with distinct.
Abercrombie, Kim 2
Abercrombie, Kim 3
Abercrombie, Kim 5
Abolrous, Hazen 2
Abolrous, Hazen 5
Abolrous, Hazen 6
Abolrous, Hazen 3
Hance, Jim 2
Hance, Jim 1
Adams, Terry 2
Adams, Terry 5
Adams, Terry 2
Hansen, Claus 3
Hansen, Claus 2
Perham, Tom 3

Join with distinct and count.
15

Selecting students with age between 10 and 15.
Abercrombie, Kim
Abolrous, Hazen
Hance, Jim
Adams, Terry
Hansen, Claus
Penor, Lori
Perham, Tom

Selecting students with age either 11 or 12.
Hance, Jim
Adams, Terry
Hansen, Claus
Perham, Tom

Selecting students in a certain age range and sorting.
Penor, Lori 13
Perham, Tom 12
Hance, Jim 12
Adams, Terry 12

Selecting students with certain ages, taking account of possibility of nulls.
Hance, Jim
Adams, Terry

Union of two queries.
Abercrombie, Kim 10
Abolrous, Hazen 14
Hance, Jim 12
Adams, Terry 12
Hansen, Claus 11
Penor, Lori 13
Perham, Tom 12
Peng, Yun-Feng NULL

Intersect of two queries.

Using if statement to alter results for special value.
1 10 10
2 14 14
3 12 12
4 12 12
5 11 11
6 13 13
7 12 12
8 NULL NULL

Using if statement to alter results special values.
1 10 10
2 14 14
3 12 12
4 12 12
5 11 11
6 13 13
7 12 12
8 NULL NULL

Multiple table select.
StudentID Name Age CourseID CourseName
1 Abercrombie, Kim 10 1 Algebra I
2 Abolrous, Hazen 14 1 Algebra I
3 Hance, Jim 12 1 Algebra I
4 Adams, Terry 12 1 Algebra I
5 Hansen, Claus 11 1 Algebra I
6 Penor, Lori 13 1 Algebra I
7 Perham, Tom 12 1 Algebra I
8 Peng, Yun-Feng NULL 1 Algebra I
1 Abercrombie, Kim 10 2 Trigonometry
2 Abolrous, Hazen 14 2 Trigonometry
3 Hance, Jim 12 2 Trigonometry
4 Adams, Terry 12 2 Trigonometry
5 Hansen, Claus 11 2 Trigonometry
6 Penor, Lori 13 2 Trigonometry
7 Perham, Tom 12 2 Trigonometry
8 Peng, Yun-Feng NULL 2 Trigonometry
1 Abercrombie, Kim 10 3 Algebra II
2 Abolrous, Hazen 14 3 Algebra II
3 Hance, Jim 12 3 Algebra II
4 Adams, Terry 12 3 Algebra II
5 Hansen, Claus 11 3 Algebra II
6 Penor, Lori 13 3 Algebra II
7 Perham, Tom 12 3 Algebra II
8 Peng, Yun-Feng NULL 3 Algebra II
1 Abercrombie, Kim 10 4 History
2 Abolrous, Hazen 14 4 History
3 Hance, Jim 12 4 History
4 Adams, Terry 12 4 History
5 Hansen, Claus 11 4 History
6 Penor, Lori 13 4 History
7 Perham, Tom 12 4 History
8 Peng, Yun-Feng NULL 4 History
1 Abercrombie, Kim 10 5 English
2 Abolrous, Hazen 14 5 English
3 Hance, Jim 12 5 English
4 Adams, Terry 12 5 English
5 Hansen, Claus 11 5 English
6 Penor, Lori 13 5 English
7 Perham, Tom 12 5 English
8 Peng, Yun-Feng NULL 5 English
1 Abercrombie, Kim 10 6 French
2 Abolrous, Hazen 14 6 French
3 Hance, Jim 12 6 French
4 Adams, Terry 12 6 French
5 Hansen, Claus 11 6 French
6 Penor, Lori 13 6 French
7 Perham, Tom 12 6 French
8 Peng, Yun-Feng NULL 6 French
1 Abercrombie, Kim 10 7 Chinese
2 Abolrous, Hazen 14 7 Chinese
3 Hance, Jim 12 7 Chinese
4 Adams, Terry 12 7 Chinese
5 Hansen, Claus 11 7 Chinese
6 Penor, Lori 13 7 Chinese
7 Perham, Tom 12 7 Chinese
8 Peng, Yun-Feng NULL 7 Chinese

Multiple Joins
Abercrombie, Kim Trigonometry
Abercrombie, Kim Algebra II
Abercrombie, Kim English
Abolrous, Hazen Trigonometry
Abolrous, Hazen English
Abolrous, Hazen French
Abolrous, Hazen Algebra II
Hance, Jim Trigonometry
Hance, Jim Algebra I
Adams, Terry Trigonometry
Adams, Terry English
Adams, Terry Trigonometry
Hansen, Claus Algebra II
Hansen, Claus Trigonometry
Perham, Tom Algebra II

Multiple Left Outer Joins
Abercrombie, Kim Trigonometry
Abercrombie, Kim Algebra II
Abercrombie, Kim English
Abolrous, Hazen Trigonometry
Abolrous, Hazen English
Abolrous, Hazen French
Abolrous, Hazen Algebra II
Hance, Jim Trigonometry
Hance, Jim Algebra I
Adams, Terry Trigonometry
Adams, Terry English
Adams, Terry Trigonometry
Hansen, Claus Algebra II
Hansen, Claus Trigonometry
Penor, Lori
Perham, Tom Algebra II
Peng, Yun-Feng

type schema
val db : schema.ServiceTypes.SimpleDataContextTypes.MyDatabase1
val student : System.Data.Linq.Table<schema.ServiceTypes.Student>
val data : int list = [1; 5; 7; 11; 18; 21]
type Nullable<'T
                when 'T : (new : unit ->  'T) and 'T : struct and
                     'T :> System.ValueType> with
  member Print : unit -> string
val num : int = 21
val student2 : schema.ServiceTypes.Student
val student3 : schema.ServiceTypes.Student
val student4 : schema.ServiceTypes.Student
val student5 : int = 1
val student6 : int = 8
val idList : int list = [1; 2; 5; 10]
val idQuery : seq<int>
val names : string [] = [|"a"; "b"; "c"|]
module Queries = begin
  val query1 : System.Linq.IQueryable<string * System.Nullable<int>>
  val query2 : System.Linq.IQueryable<string * System.Nullable<int>>
end
module Queries2 = begin
  val query1 : System.Linq.IQueryable<string * System.Nullable<int>>
  val query2 : System.Linq.IQueryable<string * System.Nullable<int>>
end

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