I am curious what is proper ordering for cross joining and joining at all for two tables. I look at the example at http://www.postgresql.org/docs/9.0/static/queries-table-expressions.html and there is:
SELECT * FROM t1 CROSS JOIN t2; num | name | num | value -----+------+-----+------- 1 | a | 1 | xxx 1 | a | 3 | yyy 1 | a | 5 | zzz 2 | b | 1 | xxx 2 | b | 3 | yyy 2 | b | 5 | zzz 3 | c | 1 | xxx 3 | c | 3 | yyy 3 | c | 5 | zzz (9 rows) I thought that this should be rather: 1 | a | 1 | xxx 2 | b | 1 | xxx 3 | c | 1 | xxx 1 | a | 3 | yyy 2 | b | 3 | yyy 2 | b | 3 | yyy 1 | a | 5 | zzz 2 | b | 5 | zzz 3 | c | 5 | zzz DROP TABLE t1, t2; CREATE TABLE t1 (num int, char name); CREATE TABLE t2 (num int, value varchar(3)); INSERT INTO t1 VALUES (1, 'a'), (2, 'b'), (3, 'c'); INSERT INTO t2 VALUES (1, 'xxx'), (2, 'yyy'), (3, 'zzz'); SELECT * FROM t1 CROSS JOIN t2; num | char | num | value -----+------+-----+------- 1 | a | 1 | xxx 2 | b | 1 | xxx 3 | c | 1 | xxx 1 | a | 2 | yyy 2 | b | 2 | yyy 3 | c | 2 | yyy 1 | a | 3 | zzz 2 | b | 3 | zzz 3 | c | 3 | zzz (9 rows) or even (same data as in documentation): DROP TABLE t1, t2; CREATE TABLE t1 (num int, char name); CREATE TABLE t2 (num int, value varchar(3)); INSERT INTO t1 VALUES (1, 'a'), (2, 'b'), (3, 'c'); INSERT INTO t2 VALUES (1, 'xxx'), (3, 'yyy'), (5, 'zzz'); SELECT * FROM t1 CROSS JOIN t2; num | char | num | value -----+------+-----+------- 1 | a | 1 | xxx 2 | b | 1 | xxx 3 | c | 1 | xxx 1 | a | 3 | yyy 2 | b | 3 | yyy 3 | c | 3 | yyy 1 | a | 5 | zzz 2 | b | 5 | zzz 3 | c | 5 | zzz (9 rows) Is there any "proper", standard ordering that I can assume for sure ? Maybe PostgreSQL 8.4/9.0 versions have strict ordering and older versions are using mixed ordering depends on something I don't know (I am just guessing). Thanks in advance. Regards, G. Sz. -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
