Cannot assign a default value to a local variable in SQL

问题

I am trying to declare local variable like:

DECLARE @thresholdDate DATETIME = '2014-11-30'

And I am getting error:

Cannot assign a default value to a local variable.

As per documentation:

DECLARE @find varchar(30); 
/* Also allowed: 
DECLARE @find varchar(30) = 'Man%'; 
*/

What I am doing wrong?

回答1:

Prior to SQL Server 2008, assigning a default value (or initial value) to a local variable is not allowed; otherwise this error message will be encountered.

Solution 1: (Use SET)

DECLARE @thresholdDate DATETIME 
set @thresholdDate = '2014-11-30'

For more details about the error : http://www.sql-server-helper.com/error-messages/msg-139.aspx

Solution 2: (Upgrade)

Another way of avoiding this error, which is a little bit a far-fetched solution, is to upgrade to SQL Server 2008. SQL Server 2008 now allows the assigning of a value to a variable in the DECLARE statement.

回答2:

You will hit this error

Cannot assign a default value to a local variable

in case you are running SQL Server 2005 or earlier, and you try to declare a variable and assign it a value in one statement.

Something like -

DECLARE @Var Varchar(15) = 'Test'

Message 139, Level 15, State 1, Line 0
Cannot assign a default value to a local variable

Variable declaration has been enhanced in SQL Server 2008 and newer versions, and I realized this today when I was deploying a code for multiple systems.

Apparently we also have the flexibility to just use one Declare statement to declare multiple variables -

DECLARE @Var Varchar(15) = 'Test',
        @Char Varchar(10) = 'Test2',
        @Char2 Varchar(10) = 'Test3'

In SQL Server 2005 or earlier, you will need to declare the variable and then assign it a value using Set statement.

Example -

DECLARE @Var Varchar(15) 
SET @Var = 'Test'

回答3:

The error

Cannot assign a default value to a local variable

occurs if you are using SQL Server 2005 while assigning default value to local variable.

For SQL Server 2005 use this code:

DECLARE @thresholdDate AS DATETIME 

SET @thresholdDate = '2014-11-30'

SELECT @thresholdDate

For SQL Server 2008 and newer you can use this instead:

DECLARE @thresholdDate DATETIME = '2014-11-30'
SELECT @thresholdDate

来源：https://stackoverflow.com/questions/27060586/cannot-assign-a-default-value-to-a-local-variable-in-sql

标签

sql

sql-server

sql-server-2005

default-value

declare