Problem with CASE Statement in T-SQL

You can't mix assignment with output in CASE statement.

You can print the output basing on the value of the @n variable using following syntax for example:

declare @n int             
set @n = 1            
            
print CASE            
    when @n=1 then 'n=1'            
    when @n=2 then 'n=2'            
    when @n=2+2 then 'n=4'            
    else            
    'n is some other value.'            
end            

Please note that each time you use variable it must be prefixed with @ and print statement contains conditional expression that determines what has to be printed. Alternatively, you can assign the output of case statement to a variable and print it:

declare @n int, @msg varchar(50)             
set @n = 1            
            
set @msg = CASE            
        when @n=1 then 'n=1'            
        when @n=2 then 'n=2'            
        when @n=2+2 then 'n=4'            
        else            
        'n is some other value.'            
    end            
            
print @msg            

When you assign a value to a variable, you have to use keyword set or select, depending on the situation.

Regards

Piotr

you should be using IF . . ELSE for flow control not CASE .. WHEN

CASE .. WHEN is to use within a QUERY