Question

I would like to do an SQL query to select from the following table:

id    type    num
1     a       3
1     b       4
2     a       5
2     c       6

In the case where they have the same ‘id’ and be type ‘a or b’, so the result would look something like this:

id    type    num
1     a       3
1     b       4

Any one has any idea how that can be accomplished?

Answer 1

SELECT table1.* 
FROM table1,
(
  SELECT COUNT(*) as cnt, id
  FROM (
    SELECT * 
    FROM table1
    WHERE type = 'a' OR type = 'b'
  ) sub1
  GROUP BY id
  HAVING cnt > 1
)sub2
WHERE table1.id = sub2.id

Tested here: http://sqlfiddle.com/#!2/4a031/1 seems to work fine.