Question

I have many tables, say T1, T2, T3.

Every table has a column named field. I’d like to get the maximum value of field in the three tables, but also from which table it came, for example:

T1 { 6, 8, 23 }
T2 { 8, 45, 23 }
T3 { 68, 5, 67 }

I have to get 68 knowing that it belongs to table T3. I use MySQL as DBMS.

Answer 1

Maybe there’s a catch I’m missing but the following seems to me a possible solution:

SELECT 'T1' AS Source, field FROM T1
UNION ALL
SELECT 'T2' AS Source, field FROM T2
UNION ALL
SELECT 'T3' AS Source, field FROM T3

ORDER BY field DESC
LIMIT 1