It's possible to select records from several sources at a time. Consider the following examples. There are two tables, each with three rows:
car_portal=> SELECT * FROM car_portal_app.a; a_int | a_text-------+-------- 1 | one 2 | two 3 | three(3 rows)car_portal=> SELECT * FROM car_portal_app.b; b_int | b_text-------+-------- 2 | two 3 | three 4 | four(3 rows)
When records are selected from both of them, we get all the possible combinations of all their rows:
car_portal=> SELECT * FROM car_portal_app.a, car_portal_app.b; a_int | a_text | b_int | b_text-------+--------+-------+-------- 1 | one | 2 | two 1 | one | 3 | three 1 | one | 4 | four 2 | two | 2 | two 2 | two | 3 | three 2 | two | 4 | four 3 | three | 2 ...
