Applying the MIN aggregate function to a BIT field

Question

I want to write the following query:

SELECT   ..., MIN(SomeBitField), ...
FROM     ...
WHERE    ...
GROUP BY ...

The problem is, SQL Ser

Answer 1

Since there are only two options for BIT, just use a case statement:

SELECT CASE WHEN EXISTS (SELECT 1 FROM ....) THEN 1 ELSE 0 END AS 'MinBit'
FROM ...
WHERE ...

This has the advantage of:

• Not forcing a table scan (indexes on BIT fields pretty much never get used)
• Short circuiting TWICE (once for EXISTS and again for the CASE)

It is a little more code to write but it shouldn't be terrible. If you have multiple values to check you could always encapsulate your larger result set (with all the JOIN and FILTER criteria) in a CTE at the beginning of the query, then reference that in the CASE statements.