In PostgreSQL, you can for instance, say, `SELECT 1, srf()`. Let's assume the SRF returns three rows, 1, 2, 3. That'll return
1,1
1,2
1,3
If the SRF returns 0 rows. that'll return no rows, Because you can't cross join 1 row, with 0 rows. an SRF in a SELECT-list is essentially a cross-join-lateral.