# Compare two query result sets

Compare matching columns in both directions when checking whether two SQL queries return the same set of rows. `EXCEPT` returns distinct rows from its left input that are absent on its right input.

```sql
CREATE TABLE expected_result(id INTEGER, value TEXT);
CREATE TABLE actual_result(id INTEGER, value TEXT);
INSERT INTO expected_result VALUES (1, 'a'), (2, 'b');
INSERT INTO actual_result VALUES (1, 'a'), (3, 'c');

SELECT id, value FROM expected_result
EXCEPT
SELECT id, value FROM actual_result;

SELECT id, value FROM actual_result
EXCEPT
SELECT id, value FROM expected_result;
```

An empty result in both directions proves equality as sets, including whole-row values. It does not prove equal duplicate counts: `EXCEPT` removes repeated copies. If duplicates are meaningful, group each input by the compared columns, include `count(*)`, and compare those grouped results in both directions.

Keep inputs fixed while comparing them. Different filters, column order, conversions or concurrent edits can explain a difference without a query bug. A final `ORDER BY` makes diagnostic output easier to read but is unnecessary for set membership.

See [`EXCEPT`](https://coordinatordb.com/docs/reference/statements/select/except) and [transactions](https://coordinatordb.com/docs/concepts/features/operations/insert/transactions).