CASE equivalent of a nested IIF statement

Question

Can anyone please decode the following nested IIF to a CASE statement in SQL.. I know IIF is allowed in SQL Server 2012 but I find it hard to get an easy grasp of a nested IIF l

Answer 1

This is old now, and there are other answers that already work, but for fun it is possible to write this as a functional expression without any CASE statements at all, like this:

char(65 + ceiling(ceiling(COALESCE(NULLIF(TABLE_A.Col_1, 0), TABLE_A.Col_2 + (2*TABLE_A.Col_3))) - .5 / 10000000000000))

There is a very small chance that the functional approach will perform noticeably better on large sets with good indexing.

Here's my proof-of-concept test script:

http://sqlfiddle.com/#!3/a95b3/2

Answer 2

CASE 
    WHEN 
     (CASE 
          WHEN TABLE_A.Col1= 0 
          THEN TABLE_A.Col2_2 + (2*TABLE_A.Col3)
          ELSE TABLE_A.Col1 
      END) <=0.5 
    THEN 'A'
    ELSE 'B'
END
AS result

Answer 3

I think this is what it boils down to in one CASE expression:

CASE
  WHEN TABLE_A.Col_1 = 0 AND TABLE_A.Col_2 + (2*TABLE_A.Col_3) <= .5 THEN 'A'
  WHEN TABLE_A.Col_1 <> 0 AND TABLE_A.Col_1 <= .5 THEN 'A'
  ELSE 'B'
END

Answer 4

This should be the equivalent:

CASE
    WHEN
        CASE
            WHEN TABLE_A.Col_1 = 0
            THEN TABLE_A.Col_2 + (2*TABLE_A.Col_3)
            ELSE TABLE_A.Col_1
        END <= .5
    THEN 'A'
    ELSE 'B'
END As Result