I’ve had to do this a couple of times and I just realized I haven’t written about it anywhere.

If you need to SELECT a field from a row that returns different content based on the content of the field, you’d think, based on previous programming experience, that your code would look something like this.


SELECT IIF(field=2,"content true","content false")

But you’d be wrong.

No, the people who created SQL thought a syntax with a little richer flexibility would do the trick.  Why limit ourselves to two states when multiple states will do?

SELECT CASE field WHEN 2 THEN "content true"
ELSE "content false" END FROM DB

In fact you can have multiple WHEN conditions in your code

    WHEN 1 THEN 'One'
    WHEN 2 THEN 'Two'
    WHEN 3 THEN 'Three'

You can also use multiple fields

   WHEN field1 = 1 THEN 'field one'
   WHEN field2 = 2 THEN 'field two'
   ELSE 'Something else'

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  • http://osusports.info Steve

    Is there a performance difference?

  • Mitch

    Yeah. IIF doesn’t perform at all. You HAVE TO use SELECT CASE if you want to do this as part of a SELECT statement in TSQL.