return count 0 with mysql group by

Question

database table like this

============================
= suburb_id   |   value
= 1           |    2
= 1           |    3
= 2           |    4
= 3           |          


        

Answer 1

This:

SELECT  id, COUNT(suburb_id)
FROM    (
        SELECT  1 AS id
        UNION ALL
        SELECT  2 AS id
        UNION ALL
        SELECT  3 AS id
        UNION ALL
        SELECT  4 AS id
        ) ids
LEFT JOIN
        suburbs s
ON      s.suburb_id = ids.id
GROUP BY
        id

or this:

SELECT  id,
        (
        SELECT  COUNT(*)
        FROM    suburb
        WHERE   suburb_id = id
        )
FROM    (
        SELECT  1 AS id
        UNION ALL
        SELECT  2 AS id
        UNION ALL
        SELECT  3 AS id
        UNION ALL
        SELECT  4 AS id
        ) ids

This article compares performance of the two approaches:

• Aggregates: subqueries vs. GROUP BY

, though it does not matter much in your case, as you are querying only 4 records.