Question

We have a requirement like fetching all the columns of a table by filtering distinct values of one column along with the max value of another column.

Example:

Table A

id name qty
__ __ __

1 Dinesh 10
2 Ramesh 8
3 Dinesh 2
4 Ganesh 3
5 Ganesh 20

Here fetching distinct name along with max(qty);

Expected output:

1 Dinesh 10
2 Ramesh 8
5 Ganesh 20

Can anyone say how to achieve this in DB2 query?

Thanks in advance

Answer 1

You could use a correlated sub-query to do this.

SELECT T.id, T.name, T.qty
FROM tableA T
WHERE T.qty = (
    SELECT MAX(qty)
    FROM tableA
    WHERE name = T.name
)

However, note that if there is another record with the same name and maximum qty (such as 6 Dinesh 10) then both records will be returned. This can be resolved be writing the query slightly differently:

SELECT T.id, T.name, T.qty
FROM tableA T
WHERE NOT EXISTS (
    SELECT 1
    FROM tableA
    WHERE name = T.name
        AND qty > T.qty
        OR (id > T.id AND qty = T.qty)
    )