Question

I’m trying to update multiple rows in a table but due to server resources being limited I can’t do it in individual UPDATE statements. I know that this can be done in a single statement by using a CASE but I’m having trouble getting this to work as the table needs to be updated using a composite key (three columns) rather than a single value.

This example works:

UPDATE myTable
    SET newValue = CASE id
        WHEN 1 THEN 'val1'
        WHEN 2 THEN 'val2'
        WHEN 3 THEN 'val3'
    END,
WHERE id IN (1,2,3)

But I need something like this to work:

UPDATE myTable
    SET newValue = CASE (id,x,y)
        WHEN (1,1,1) THEN 'val1'
        WHEN (1,1,2) THEN 'val2'
        WHEN (1,1,3) THEN 'val3'
    END,
WHERE id IN (1,2,3)

Is there a way to have something like this in a single UPDATE statement or am I going to have to work around the limited server resources?

Answer 1

Slightly refactored from your example:

UPDATE myTable
  SET newValue = CASE
    WHEN id=1 AND x=1 AND y=1 THEN 'val1'
    WHEN id=1 AND x=1 AND y=2 THEN 'val2'
    WHEN id=1 AND x=1 AND y=3 THEN 'val3'
    END
WHERE id IN (1,2,3)