case statement in SQL, how to return multiple variables?

Question

I would like to return multiple values in my case statement, such as :

SELECT
  CASE
    WHEN  THEN 
    WHEN          


        

Answer 1

The basic way, unfortunately, is to repeat yourself.

SELECT
  CASE WHEN  THEN  WHEN  THEN  ELSE  END,
  CASE WHEN  THEN  WHEN  THEN  ELSE  END
FROM 
  
Fortunately, most RDBMS are clever enough to NOT have to evaluate the conditions multiple times.  It's just redundant typing.

In MS SQL Server (2005+) you could possible use CROSS APPLY as an alternative to this.  Though I have no idea how performant it is...
SELECT
  *
FROM
  

CROSS APPLY
  (
   SELECT a1, b1 WHERE 
   UNION ALL
   SELECT a2, b2 WHERE 
   UNION ALL
   SELECT a3, b3 WHERE 
  )
  AS case_proxy
The noticable downside here is that there is no ELSE equivalent and as all the conditions could all return values, they need to be framed such that only one can ever be true at a time.

EDIT
If Yuck's answer is changed to a UNION rather than JOIN approach, it becomes very similar to this.  The main difference, however, being that this only scans the input data set once, rather than once per condition (100 times in your case).

EDIT
I've also noticed that you may mean that the values returned by the CASE statements are fixed.  All records that match the same condition get the exact sames values in value1 and value2.  This could be formed like this...
WITH
  checked_data AS
(
  SELECT
    CASE WHEN  THEN 1
         WHEN  THEN 2
         WHEN  THEN 3
         ...
         ELSE                   100
    END AS condition_id,
    *
  FROM
    

)
,
  results (condition_id, value1, value2) AS
(
   SELECT 1, a1, b1
   UNION ALL
   SELECT 2, a2, b2
   UNION ALL
   SELECT 3, a3, b3
   UNION ALL
   ...
   SELECT 100, a100, b100
)
SELECT
  *
FROM
  checked_data
INNER JOIN
  results
    ON results.condition_id = checked_data.condition_id

                                                        

              
                
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