Agregat yang Ditentukan Pengguna CLR - Fungsi Pemanggilan

Artikel
07/04/2024

Berlaku untuk: SQL Server

Dalam pernyataan TRANSACT-SQL SELECT, Anda dapat memanggil agregat yang ditentukan pengguna common language runtime (CLR), tunduk pada semua aturan yang berlaku untuk fungsi agregat sistem.

Aturan tambahan berikut berlaku:

Pengguna saat ini harus memiliki izin EXECUTE pada agregat yang ditentukan pengguna.
Agregat yang ditentukan pengguna harus dipanggil menggunakan nama dua bagian dalam bentuk schema_name.udagg_name.
Jenis argumen agregat yang ditentukan pengguna harus cocok atau secara implisit dapat dikonversi ke input_type agregat, seperti yang didefinisikan dalam pernyataan CREATE AGGREGATE .
Jenis pengembalian agregat yang ditentukan pengguna harus cocok dengan return_type dalam pernyataan CREATE AGGREGATE .

Contoh 1

Berikut ini adalah contoh fungsi agregat yang ditentukan pengguna yang menggabungkan sekumpulan nilai string yang diambil dari kolom dalam tabel:

[C#]

using System;  
using System.Data;  
using Microsoft.SqlServer.Server;  
using System.Data.SqlTypes;  
using System.IO;  
using System.Text;  
  
[Serializable]  
[SqlUserDefinedAggregate(  
    Format.UserDefined, //use clr serialization to serialize the intermediate result  
    IsInvariantToNulls = true, //optimizer property  
    IsInvariantToDuplicates = false, //optimizer property  
    IsInvariantToOrder = false, //optimizer property  
    MaxByteSize = 8000) //maximum size in bytes of persisted value  
]  
public class Concatenate : IBinarySerialize  
{  
    /// <summary>  
    /// The variable that holds the intermediate result of the concatenation  
    /// </summary>  
    public StringBuilder intermediateResult;  
  
    /// <summary>  
    /// Initialize the internal data structures  
    /// </summary>  
    public void Init()  
    {  
        this.intermediateResult = new StringBuilder();  
    }  
  
    /// <summary>  
    /// Accumulate the next value, not if the value is null  
    /// </summary>  
    /// <param name="value"></param>  
    public void Accumulate(SqlString value)  
    {  
        if (value.IsNull)  
        {  
            return;  
        }  
  
        this.intermediateResult.Append(value.Value).Append(',');  
    }  
  
    /// <summary>  
    /// Merge the partially computed aggregate with this aggregate.  
    /// </summary>  
    /// <param name="other"></param>  
    public void Merge(Concatenate other)  
    {  
        this.intermediateResult.Append(other.intermediateResult);  
    }  
  
    /// <summary>  
    /// Called at the end of aggregation, to return the results of the aggregation.  
    /// </summary>  
    /// <returns></returns>  
    public SqlString Terminate()  
    {  
        string output = string.Empty;  
        //delete the trailing comma, if any  
        if (this.intermediateResult != null  
            && this.intermediateResult.Length > 0)  
        {  
            output = this.intermediateResult.ToString(0, this.intermediateResult.Length - 1);  
        }  
  
        return new SqlString(output);  
    }  
  
    public void Read(BinaryReader r)  
    {  
        intermediateResult = new StringBuilder(r.ReadString());  
    }  
  
    public void Write(BinaryWriter w)  
    {  
        w.Write(this.intermediateResult.ToString());  
    }  
}

[Visual Basic]

Imports System  
Imports System.Data  
Imports Microsoft.SqlServer.Server  
Imports System.Data.SqlTypes  
Imports System.IO  
Imports System.Text  
  
<Serializable(), SqlUserDefinedAggregate(Format.UserDefined, IsInvariantToNulls:=True, IsInvariantToDuplicates:=False, IsInvariantToOrder:=False, MaxByteSize:=8000)> _  
Public Class Concatenate  
    Implements IBinarySerialize  
  
    ''' <summary>  
    ''' The variable that holds the intermediate result of the concatenation  
    ''' </summary>  
    Public intermediateResult As StringBuilder  
  
    ''' <summary>  
    ''' Initialize the internal data structures  
    ''' </summary>  
    Public Sub Init()  
        Me.intermediateResult = New StringBuilder()  
    End Sub  
  
    ''' <summary>  
    ''' Accumulate the next value, not if the value is null  
    ''' </summary>  
    ''' <param name="value"></param>  
    Public Sub Accumulate(ByVal value As SqlString)  
        If value.IsNull Then  
            Return  
        End If  
  
        Me.intermediateResult.Append(value.Value).Append(","c)  
    End Sub  
    ''' <summary>  
    ''' Merge the partially computed aggregate with this aggregate.  
    ''' </summary>  
    ''' <param name="other"></param>  
    Public Sub Merge(ByVal other As Concatenate)  
        Me.intermediateResult.Append(other.intermediateResult)  
    End Sub  
  
    ''' <summary>  
    ''' Called at the end of aggregation, to return the results of the aggregation.  
    ''' </summary>  
    ''' <returns></returns>  
    Public Function Terminate() As SqlString  
        Dim output As String = String.Empty  
  
        'delete the trailing comma, if any  
        If Not (Me.intermediateResult Is Nothing) AndAlso Me.intermediateResult.Length > 0 Then  
            output = Me.intermediateResult.ToString(0, Me.intermediateResult.Length - 1)  
        End If  
  
        Return New SqlString(output)  
    End Function  
  
    Public Sub Read(ByVal r As BinaryReader) Implements IBinarySerialize.Read  
        intermediateResult = New StringBuilder(r.ReadString())  
    End Sub  
  
    Public Sub Write(ByVal w As BinaryWriter) Implements IBinarySerialize.Write  
        w.Write(Me.intermediateResult.ToString())  
    End Sub  
End Class

Setelah mengkompilasi kode ke dalam MyAgg.dll, Anda dapat mendaftarkan agregat di SQL Server sebagai berikut:

CREATE ASSEMBLY MyAgg FROM 'C:\MyAgg.dll';  
GO  
CREATE AGGREGATE MyAgg (@input nvarchar(200)) RETURNS nvarchar(max)  
EXTERNAL NAME MyAgg.Concatenate;

Catatan

Objek database Visual C++, seperti fungsi bernilai skalar, yang telah dikompilasi dengan opsi kompilator /clr:pure tidak didukung untuk eksekusi di SQL Server.

Seperti kebanyakan agregat, sebagian besar logika berada dalam metode Akumulasi . Di sini, string yang diteruskan sebagai parameter ke metode Akumulasi ditambahkan ke objek StringBuilder yang diinisialisasi dalam metode Init. Dengan asumsi bahwa ini bukan pertama kalinya metode Akumulasi dipanggil, koma juga ditambahkan ke StringBuilder sebelum menambahkan string yang diteruskan. Pada kesimpulan tugas komputasi, metode Penghentian dipanggil, yang mengembalikan StringBuilder sebagai string.

Misalnya, pertimbangkan tabel dengan skema berikut:

CREATE TABLE BookAuthors  
(  
   BookID   int       NOT NULL,  
   AuthorName    nvarchar(200) NOT NULL  
);

Lalu sisipkan baris berikut:

INSERT BookAuthors VALUES(1, 'Johnson'),(2, 'Taylor'),(3, 'Steven'),(2, 'Mayler'),(3, 'Roberts'),(3, 'Michaels');

Kueri berikut kemudian akan menghasilkan hasil berikut:

SELECT BookID, dbo.MyAgg(AuthorName)  
FROM BookAuthors  
GROUP BY BookID;

BookID	Nama Penulis
1	Johnson
2	Taylor, Mayler
3	Roberts, Michaels, Steven

Contoh 2

Sampel berikut menunjukkan agregat yang memiliki dua parameter pada metode Akumulasi .

[C#]

using System;  
using System.Data;  
using System.Data.SqlClient;  
using System.Data.SqlTypes;  
using Microsoft.SqlServer.Server;  
  
[Serializable]  
[SqlUserDefinedAggregate(  
    Format.Native,  
    IsInvariantToDuplicates = false,  
    IsInvariantToNulls = true,  
    IsInvariantToOrder = true,  
    IsNullIfEmpty = true,  
    Name = "WeightedAvg")]  
public struct WeightedAvg  
{  
    /// <summary>  
    /// The variable that holds the intermediate sum of all values multiplied by their weight  
    /// </summary>  
    private long sum;  
  
    /// <summary>  
    /// The variable that holds the intermediate sum of all weights  
    /// </summary>  
    private int count;  
  
    /// <summary>  
    /// Initialize the internal data structures  
    /// </summary>  
    public void Init()  
    {  
        sum = 0;  
        count = 0;  
    }  
  
    /// <summary>  
    /// Accumulate the next value, not if the value is null  
    /// </summary>  
    /// <param name="Value">Next value to be aggregated</param>  
    /// <param name="Weight">The weight of the value passed to Value parameter</param>  
    public void Accumulate(SqlInt32 Value, SqlInt32 Weight)  
    {  
        if (!Value.IsNull && !Weight.IsNull)  
        {  
            sum += (long)Value * (long)Weight;  
            count += (int)Weight;  
        }  
    }  
  
    /// <summary>  
    /// Merge the partially computed aggregate with this aggregate  
    /// </summary>  
    /// <param name="Group">The other partial results to be merged</param>  
    public void Merge(WeightedAvg Group)  
    {  
        sum += Group.sum;  
        count += Group.count;  
    }  
  
    /// <summary>  
    /// Called at the end of aggregation, to return the results of the aggregation.  
    /// </summary>  
    /// <returns>The weighted average of all inputed values</returns>  
    public SqlInt32 Terminate()  
    {  
        if (count > 0)  
        {  
            int value = (int)(sum / count);  
            return new SqlInt32(value);  
        }  
        else  
        {  
            return SqlInt32.Null;  
        }  
    }  
}

[Visual Basic]

Imports System  
Imports System.Data  
Imports System.Data.SqlClient  
Imports System.Data.SqlTypes  
Imports Microsoft.SqlServer.Server  
Imports System.Runtime.InteropServices  
  
<StructLayout(LayoutKind.Sequential)> _  
<Serializable(), SqlUserDefinedAggregate(Format.Native, _  
IsInvariantToDuplicates:=False, _  
IsInvariantToNulls:=True, _  
IsInvariantToOrder:=True, _  
IsNullIfEmpty:=True, _  
Name:="WeightedAvg")> _  
Public Class WeightedAvg  
  
    ''' <summary>  
    ''' The variable that holds the intermediate sum of all values multiplied by their weight  
    ''' </summary>  
    Private sum As Long  
  
    ''' <summary>  
    ''' The variable that holds the intermediate sum of all weights  
    ''' </summary>  
    Private count As Integer  
  
    ''' <summary>  
    ''' The variable that holds the intermediate sum of all weights  
    ''' </summary>  
    Public Sub Init()  
        sum = 0  
        count = 0  
    End Sub  
  
    ''' <summary>  
    ''' Accumulate the next value, not if the value is null  
    ''' </summary>  
    ''' <param name="Value">Next value to be aggregated</param>  
    ''' <param name="Weight">The weight of the value passed to Value parameter</param>  
    Public Sub Accumulate(ByVal Value As SqlInt32, ByVal Weight As SqlInt32)  
        If Not Value.IsNull AndAlso Not Weight.IsNull Then  
            sum += CType(Value, Long) * CType(Weight, Long)  
            count += CType(Weight, Integer)  
        End If  
    End Sub  
  
    ''' <summary>  
    ''' Merge the partially computed aggregate with this aggregate.  
    ''' </summary>  
    ''' <param name="Group">The other partial results to be merged</param>  
    Public Sub Merge(ByVal Group As WeightedAvg)  
        sum = Group.sum  
        count = Group.count  
    End Sub  
  
    ''' <summary>  
    ''' Called at the end of aggregation, to return the results of the aggregation.  
    ''' </summary>  
    ''' <returns>The weighted average of all inputed values</returns>  
    Public Function Terminate() As SqlInt32  
        If count > 0 Then  
            ''                        int value = (int)(sum / count);  
            ''          return new SqlInt32(value);  
            Dim value As Integer = CType(sum / count, Integer)  
            Return New SqlInt32(value)  
        Else  
            Return SqlInt32.Null  
        End If  
    End Function  
End Class

Setelah Anda mengkompilasi kode sumber C# atau Visual Basic, jalankan Transact-SQL berikut. Skrip ini mengasumsikan bahwa DLL disebut WghtAvg.dll dan berada di direktori akar drive C Anda. Database yang disebut pengujian juga diasumsikan.

use test;  
go  
  
-- sp_configure 'clr enabled', 1;  
-- go  
  
--- RECONFIGURE WITH OVERRIDE;  
-- go  
  
IF EXISTS (SELECT name FROM systypes WHERE name = 'MyTableType')  
   DROP TYPE MyTableType;  
go  
  
IF EXISTS (SELECT name FROM sysobjects WHERE name = 'WeightedAvg')  
   DROP AGGREGATE WeightedAvg;  
go  
  
IF EXISTS (SELECT name FROM sys.assemblies WHERE name = 'MyClrCode')  
   DROP ASSEMBLY MyClrCode;  
go  
  
CREATE ASSEMBLY MyClrCode FROM 'C:\WghtAvg.dll';  
GO  
  
CREATE AGGREGATE WeightedAvg (@value int, @weight int) RETURNS int  
EXTERNAL NAME MyClrCode.WeightedAvg;  
go  
  
CREATE TYPE MyTableType AS table (ItemValue int, ItemWeight int);  
go  
  
DECLARE @myTable AS MyTableType;  
  
INSERT INTO @myTable VALUES(1, 4), (6, 1);  
  
SELECT dbo.WeightedAvg(ItemValue, ItemWeight) FROM @myTable;  
go

Lihat Juga

Agregat yang Ditentukan Pengguna CLR

Bagikan melalui

Agregat yang Ditentukan Pengguna CLR - Fungsi Pemanggilan

Contoh 1

Contoh 2

Lihat Juga

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