Question

I’m doing an insert, and one of the values I’m inserting is calculated as follows:

SUM(Value1)/(
    CASE SUM(
        CASE Value2 > 0 
        THEN 1
        ELSE 0 
        END
    ) = 0 
    THEN 1 
    ELSE SUM(
        CASE Value2 > 0 
        THEN 1 
        ELSE 0 
        END
    )
)

The inner CASE-part is duplicated twice, it would be nice to set an alias or variable to this value and use that alias or variable instead.

Answer 1

CTE answer…

WITH
  step1 AS
(
  SELECT
    SUM(value1)                            AS interimValue1
    SUM(CASE value2 > 0 THEN 1 ELSE 0 END) AS interimValue2,
    <other fields>
  FROM
    <a query>
)
SELECT
  interimValue / CASE interimValue2 = 0 THEN 1 ELSE interimValue2 END
FROM
  step1

SubQuery version…

SELECT
  interimValue / CASE interimValue2 = 0 THEN 1 ELSE interimValue2 END
FROM
(
  SELECT
    SUM(value1)                            AS interimValue1
    SUM(CASE value2 > 0 THEN 1 ELSE 0 END) AS interimValue2,
    <other fields>
  FROM
    <a query>
)
  AS step1

Or, more specific to the SQL you posted, but not an answer to the generic case…

SUM(value1) / COALESCE(SUM(CASE WHEN value2 > 0 THEN 1 ELSE NULL END), 1)

(Returning NULL where you return 0 allows COALESCE to replace NULLs with 1s.)