Question

I need to perform a group by, but only on rows that meet a condition, otherwise return all rows that do not meet the condition. For example, in the following table, I want to group only rows that have ‘1’ in the “active” field, and return all rows that do not.

TABLE (id, label, active):

1, A, 1
2, A, 1
3, B, 0
4, B, 0

Would return:

1, A, 1
3, B, 0
4, B, 0

Answer 1

Here is the simplest way I can think of. It is a case statement in the group by. If the condition is met then group by the label, otherwise group by the primary key.

SELECT id, label, active
FROM table
GROUP BY
  CASE
    WHEN active = 1 THEN active
    ELSE id END

If you want to group by active and label:

SELECT id, label, active
FROM table
GROUP BY
  CASE
    WHEN active = 1 THEN active
    ELSE id END,
  label

EDIT: I misunderstood which field you want to group on. Corrected now.