IF condition doesn't work properly

Question

I would like to write a query using

IF

, but its not working , what's wrong with this query?

SELECT

IF(Emp.Name is not null)     

        ((Emp.Name) + '_' + (Emp.LastName)) as ID

else

   Emp.ID

I get this error:

Incorrect syntax near the keyword 'IF'.

Why is that?

Thank you.

Answer 1

You can use CASE EXPRESSION :

SELECT CASE WHEN emp.name is not null THEN emp.name + '_' + emp.lastName 
            ELSE Emp.id 
       END as [ID]
FROM ...

The IF() is performed differently in SQL-Server (I assume by the concat syntax),

IF ( Condition ) 
    SQL STATEMENT
ELSE
    SQL STATEMENT

Which means you need to perform the entire select in each block. Your kind of IF() is used in MySQL , IF(Condition , THEN , ELSE )

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