Lack of integration tests for SQL catalog implementation

[callum-ryan]

Following on from #610, #534, #524 and #610 (review) from @liurenjie1024.

The current test suite only runs against SQLite, for the catalog implementation to be robustly tested this should be extended to both PostgreSQL and MySQL.

I've already made a start on this, so happy to take this on!

[liurenjie1024]

Thanks @callum-ryan !