SELECT * FROM t1 AS alias1, t2 AS alias2 

WHERE EXISTS ( 

  SELECT 1 FROM t2 WHERE b = alias1.a AND b > alias2.b 

) OR a = 5

revision-id: sanja@askmonty.org-20120718105902-imt07qp0v913sqa4

date: 2012-07-18 13:59:02 +0300

build-date: 2012-07-19 19:49:58 +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	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where

Warnings:

Note	1276	Field or reference 'test.alias1.a' of SELECT #2 was resolved in SELECT #1

Note	1276	Field or reference 'test.alias2.b' of SELECT #2 was resolved in SELECT #1

Note	1003	select `test`.`alias1`.`a` AS `a`,`test`.`alias2`.`b` AS `b` from `test`.`t1` `alias1` join `test`.`t2` `alias2` where (<in_optimizer>(`test`.`alias1`.`a`,<exists>(select `test`.`t2`.`b` from `test`.`t2` where ((`test`.`t2`.`b` > `test`.`alias2`.`b`) and (<cache>(`test`.`alias1`.`a`) = `test`.`t2`.`b`)))) or (`test`.`alias1`.`a` = 5))

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	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where

Warnings:

Note	1276	Field or reference 'test.alias1.a' of SELECT #2 was resolved in SELECT #1

Note	1276	Field or reference 'test.alias2.b' of SELECT #2 was resolved in SELECT #1

Note	1003	select `test`.`alias1`.`a` AS `a`,`test`.`alias2`.`b` AS `b` from `test`.`t1` `alias1` join `test`.`t2` `alias2` where (<expr_cache><`test`.`alias1`.`a`,`test`.`alias2`.`b`>(<in_optimizer>(`test`.`alias1`.`a`,<exists>(select `test`.`t2`.`b` from `test`.`t2` where ((`test`.`t2`.`b` > `test`.`alias2`.`b`) and (<cache>(`test`.`alias1`.`a`) = `test`.`t2`.`b`))))) or (`test`.`alias1`.`a` = 5))

CREATE TABLE t1 (a INT);

INSERT INTO t1 VALUES (2),(3);

CREATE TABLE t2 (b INT);

INSERT INTO t2 VALUES (1),(3);                   

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

SELECT * FROM t1 AS alias1, t2 AS alias2 

WHERE EXISTS ( 

  SELECT 1 FROM t2 WHERE b = alias1.a AND b > alias2.b 

) OR a = 5;

a	b

3	1

a	b