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SELECT @local_variable (Transact-SQL)

 

THIS TOPIC APPLIES TO:yesSQL Server (starting with 2008)yesAzure SQL DatabasenoAzure SQL Data Warehouse noParallel Data Warehouse

Sets a local variable to the value of an expression.

For assigning variables, we recommend that you use SET @local_variable instead of SELECT @local_variable.

Topic link icon Transact-SQL Syntax Conventions

-- Syntax for SQL Server and Azure SQL Database  
    
SELECT { @local_variable { = | += | -= | *= | /= | %= | &= | ^= | |= } expression } [ ,...n ] [ ; ]  

@local_variable
Is a declared variable for which a value is to be assigned.

=
Assign the value on the right to the variable on the left.

{= | += | -= | *= | /= | %= | &= | ^= | |= }
Compound assignment operator:

+= Add and assign

-= Subtract and assign

*= Multiply and assign

/= Divide and assign

%= Modulo and assign

&= Bitwise AND and assign

^= Bitwise XOR and assign

|= Bitwise OR and assign

expression
Is any valid expression. This includes a scalar subquery.

SELECT @local_variable is typically used to return a single value into the variable. However, when expression is the name of a column, it can return multiple values. If the SELECT statement returns more than one value, the variable is assigned the last value that is returned.

If the SELECT statement returns no rows, the variable retains its present value. If expression is a scalar subquery that returns no value, the variable is set to NULL.

One SELECT statement can initialize multiple local variables.

System_CAPS_ICON_note.jpg Note


A SELECT statement that contains a variable assignment cannot be used to also perform typical result set retrieval operations.

A. Use SELECT @local_variable to return a single value

In the following example, the variable @var1 is assigned Generic Name as its value. The query against the Store table returns no rows because the value specified for CustomerID does not exist in the table. The variable retains the Generic Name value.

-- Uses AdventureWorks    
  
DECLARE @var1 varchar(30);         
SELECT @var1 = 'Generic Name';         
SELECT @var1 = Name         
FROM Sales.Store         
WHERE CustomerID = 1000 ;        
SELECT @var1 AS 'Company Name';  

Here is the result set.

Company Name

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

Generic Name

B. Use SELECT @local_variable to return null

In the following example, a subquery is used to assign a value to @var1. Because the value requested for CustomerID does not exist, the subquery returns no value and the variable is set to NULL.

-- Uses AdventureWorks  
  
DECLARE @var1 varchar(30)   
SELECT @var1 = 'Generic Name'   
SELECT @var1 = (SELECT Name   
FROM Sales.Store   
WHERE CustomerID = 1000)   
SELECT @var1 AS 'Company Name' ;  

Here is the result set.

Company Name

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

NULL

DECLARE @local_variable (Transact-SQL)
Expressions (Transact-SQL)
SELECT (Transact-SQL)

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