SELECT STRAIGHT_JOIN * FROM t1 AS alias1, t1 AS alias2 
WHERE EXISTS ( SELECT 1 FROM t1 WHERE b < alias2.b AND a = alias1.a )

revision-id: sanja@askmonty.org-20120718105902-imt07qp0v913sqa4
date: 2012-07-18 13:59:02 +0300
build-date: 2012-07-19 21:33:12 +0400
revno: 3466

index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on,extended_keys=off,exists_to_in=on

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	PRIMARY	alias1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
1	PRIMARY	alias2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using join buffer (flat, BNL join)
2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
Warnings:
Note	1276	Field or reference 'test.alias2.b' of SELECT #2 was resolved in SELECT #1
Note	1276	Field or reference 'test.alias1.a' of SELECT #2 was resolved in SELECT #1
Note	1003	select straight_join `test`.`alias1`.`a` AS `a`,`test`.`alias1`.`b` AS `b`,`test`.`alias2`.`a` AS `a`,`test`.`alias2`.`b` AS `b` from `test`.`t1` `alias1` join `test`.`t1` `alias2` where <in_optimizer>(`test`.`alias1`.`a`,<exists>(select `test`.`t1`.`a` from `test`.`t1` where ((`test`.`t1`.`b` < `test`.`alias2`.`b`) and (<cache>(`test`.`alias1`.`a`) = `test`.`t1`.`a`))))

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	PRIMARY	alias1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
1	PRIMARY	alias2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using join buffer (flat, BNL join)
2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
Warnings:
Note	1276	Field or reference 'test.alias2.b' of SELECT #2 was resolved in SELECT #1
Note	1276	Field or reference 'test.alias1.a' of SELECT #2 was resolved in SELECT #1
Note	1003	select straight_join `test`.`alias1`.`a` AS `a`,`test`.`alias1`.`b` AS `b`,`test`.`alias2`.`a` AS `a`,`test`.`alias2`.`b` AS `b` from `test`.`t1` `alias1` join `test`.`t1` `alias2` where <expr_cache><`test`.`alias1`.`a`,`test`.`alias2`.`b`>(<in_optimizer>(`test`.`alias1`.`a`,<exists>(select `test`.`t1`.`a` from `test`.`t1` where ((`test`.`t1`.`b` < `test`.`alias2`.`b`) and (<cache>(`test`.`alias1`.`a`) = `test`.`t1`.`a`)))))

SET optimizer_switch = 'exists_to_in=on,in_to_exists=on';

CREATE TABLE t1 (a INT, b VARCHAR(1) NOT NULL);
INSERT INTO t1 VALUES (1,'s'),(2,'e');

SELECT STRAIGHT_JOIN * FROM t1 AS alias1, t1 AS alias2 
WHERE EXISTS ( SELECT 1 FROM t1 WHERE b < alias2.b AND a = alias1.a );

a	b	a	b
2	e	1	s

a	b	a	b
1	s	1	s
2	e	1	s
1	s	2	e
2	e	2	e