MAX (Transact-SQL)

Artikel
05/16/2013

Returns the maximum value in the expression. May be followed by the OVER clause.

Topic link icon Transact-SQL Syntax Conventions

Syntax

MAX ( [ ALL | DISTINCT ] expression )

Arguments

ALL
Applies the aggregate function to all values. ALL is the default.
DISTINCT
Specifies that each unique value is considered. DISTINCT is not meaningful with MAX and is available for ISO compatibility only.
expression
Is a constant, column name, or function, and any combination of arithmetic, bitwise, and string operators. MAX can be used with numeric, character, uniqueidentifier, and datetime columns, but not with bit columns. Aggregate functions and subqueries are not permitted.

For more information, see Expressions (Transact-SQL).

Return Types

Returns a value same as expression.

Remarks

MAX ignores any null values.

For character columns, MAX finds the highest value in the collating sequence.

Examples

A. Simple example

The following example returns the highest (maximum) tax rate.

USE AdventureWorks2012;
GO
SELECT MAX(TaxRate)
FROM Sales.SalesTaxRate;
GO

Here is the result set.

-------------------

19.60

Warning, null value eliminated from aggregate.

(1 row(s) affected)

B. Using the OVER clause

The following example uses the MIN, MAX, AVG and COUNT functions with the OVER clause to provide aggregated values for each department in the HumanResources.Department table.

USE AdventureWorks2012; 
GO
SELECT DISTINCT Name
       , MIN(Rate) OVER (PARTITION BY edh.DepartmentID) AS MinSalary
       , MAX(Rate) OVER (PARTITION BY edh.DepartmentID) AS MaxSalary
       , AVG(Rate) OVER (PARTITION BY edh.DepartmentID) AS AvgSalary
       ,COUNT(edh.BusinessEntityID) OVER (PARTITION BY edh.DepartmentID) AS EmployeesPerDept
FROM HumanResources.EmployeePayHistory AS eph
JOIN HumanResources.EmployeeDepartmentHistory AS edh
     ON eph.BusinessEntityID = edh.BusinessEntityID
JOIN HumanResources.Department AS d
 ON d.DepartmentID = edh.DepartmentID
WHERE edh.EndDate IS NULL
ORDER BY Name;

Here is the result set.

Name                          MinSalary             MaxSalary             AvgSalary             EmployeesPerDept
----------------------------- --------------------- --------------------- --------------------- ----------------
Document Control              10.25                 17.7885               14.3884               5
Engineering                   32.6923               63.4615               40.1442               6
Executive                     39.06                 125.50                68.3034               4
Facilities and Maintenance    9.25                  24.0385               13.0316               7
Finance                       13.4615               43.2692               23.935                10
Human Resources               13.9423               27.1394               18.0248               6
Information Services          27.4038               50.4808               34.1586               10
Marketing                     13.4615               37.50                 18.4318               11
Production                    6.50                  84.1346               13.5537               195
Production Control            8.62                  24.5192               16.7746               8
Purchasing                    9.86                  30.00                 18.0202               14
Quality Assurance             10.5769               28.8462               15.4647               6
Research and Development      40.8654               50.4808               43.6731               4
Sales                         23.0769               72.1154               29.9719               18
Shipping and Receiving        9.00                  19.2308               10.8718               6
Tool Design                   8.62                  29.8462               23.5054               6

 (16 row(s) affected)

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