A quick post today. SQL allows you to set many variables at the same time using a select statement. However, many people do not realize that when you do this the order the variables are set in the select statement actually matters.

Consider the following:

DECLARE @s VARCHAR(5),

@t VARCHAR(5);

SELECT @s = ‘test’,

@t = @s;

PRINT @t;

This will result in the expected output of @t = ‘test’

However, reversing the order.

DECLARE @s VARCHAR(5),

@t VARCHAR(5);

SELECT @t = @s,

@s = ‘test’;

PRINT @t;

We get the result @t = NULL

Has this every caused you an issue when triaging an issue?

Let us know in the comments below?