Question

Is there a way to simplify these two statements into one?

UPDATE items
SET D1 = 'AAA'
WHERE D1 = 'BBB'

UPDATE items
SET D2 = 'AAA'
WHERE D2 = 'BBB'

I want to set D1 to AAA ONLY IF D1 is BBB, and D2 to AAA only if D2 is BBB.

Answer 1

This is about the most efficient way you can do this in one statement:

UPDATE items
SET D1 = IF(D1 = 'BBB', 'AAA', D1),
    D2 = IF(D2 = 'BBB', 'AAA', D2)
WHERE D1 = 'BBB' OR D2 = 'BBB';

For the best performance, make sure you have separate indexes on D1 and D2. The query planner can do an index merge in this case. Don’t use only a multi-column index, or the query planner will have to fall back on a table scan.