Question

How can I select which table each result is from, when I use a UNION command to search multiple tables?

For example, if there are results from both tables, how can I add a column that will say (or differentiate between) whether it is from tableA or tableB.

Answer 1

try this one, simply add a virtual column for the name of the table.

SELECT *
FROM
(
    SELECT *, 'tableA' as tableName FROM tableA
    UNION ALL
    SELECT *, 'tableB' as tableName FROM tableB
    UNION ALL
    SELECT *, 'tableC' as tableName FROM tableC
) s
WHERE   colName = 'hello'