Specifying a join order v16
ORDERED directive to instruct the query optimizer to join tables in the order in which they're listed in the
FROM clause. If you don't include the
ORDERED keyword, the query optimizer chooses the order in which to join the tables.
For example, the following command allows the optimizer to choose the order in which to join the tables listed in the
The following command instructs the optimizer to join the tables in the order specified:
ORDERED version of the command, EDB Postgres Advanced Server first joins
emp e with
dept d before joining the results with
jobhist h. Without the
ORDERED directive, the query optimizer selects the join order.
ORDERED directive doesn't work for Oracle-style outer joins (joins that contain a + sign).