QUERY PLAN
Nested Loop Left Join (cost=0.28..16.75 rows=1 width=3912)
-> Index Scan using tbl_clients_pkey on tbl_clients c (cost=0.14..8.15 rows=1 width=3808)
Index Cond: (id = 1)
-> Index Scan using tbl_client_classes_pkey on tbl_client_classes cl (cost=0.14..8.16 rows=1 width=44)
Index Cond: (id = c.client_class)