SQL Server 2008 - Case / If statements in SELECT Clause [duplicate]

Question

I have a Query that's supposed to run like this -

If(var = xyz) 
   SELECT col1, col2
ELSE IF(var = zyx)
   SELECT col2, col3
ELSE
   SELECT col7,col8

FROM 

.
.
.

How do I achieve this in T-SQL without writing separate queries for each clause? Currently I'm running it as

IF (var = xyz) {
  Query1
}
ELSE IF (var = zyx) {
  Query2
}
ELSE {
  Query3
}

That's just a lot of redundant code just to select different columns depending on a value. Any alternatives?

Answer 1

You are looking for the CASE statement

http://msdn.microsoft.com/en-us/library/ms181765.aspx

Example copied from MSDN:

USE AdventureWorks;
GO
SELECT   ProductNumber, Category =
      CASE ProductLine
         WHEN 'R' THEN 'Road'
         WHEN 'M' THEN 'Mountain'
         WHEN 'T' THEN 'Touring'
         WHEN 'S' THEN 'Other sale items'
         ELSE 'Not for sale'
      END,
   Name
FROM Production.Product
ORDER BY ProductNumber;
GO