Question

I have two SQLite (also MySQL could be fine) databases with same table structures but different datas and I have to get all rows from one and check, one by one, if they’re exactly (same data) contained in the second one.

I need to do this for having a final yes/no/partial report (and in second step, insert in the second database the “no” and update the “partial”).

Anyone know if is there a “smart” method to do this?

Answer 1

SELECT COUNT(*) num_mismatch
FROM table1 JOIN table2 ON (..whatever the unique ID you use for matching is...)
WHERE table1.col1 != table2.col1 OR table1.col2 != table2.col2 OR ......etc.

If num_mismatch is not 0 you have mismatches. You can also change COUNT(*) to output the IDs that don’t match. It’s also possible to use NOT EXISTS and return a bit faster if there are mismatches since it will stop checking after the first mismatch.