How to verify if two tables have exactly the same data?

Question

Basically, we have one table (original table) and it is backed up into another table (backup table); thus the two tables have exactly the same sche

Answer 1

Try the following to compare two tables:

SELECT 'different' FROM DUAL WHERE EXISTS(
    SELECT * FROM (
        SELECT /*DISTINCT*/ +1 AS chk,a.c1,a.c2,a.c3 FROM a
        UNION ALL
        SELECT /*DISTINCT*/ +1 AS chk,b.c1,b.c2,b.c3 FROM b
    ) c
    GROUP BY c1,c2,c3
    HAVING SUM(chk)<>2
)
UNION SELECT 'equal' FROM DUAL
LIMIT 1;