EXPLAIN SELECT * 
FROM t1 AS alias1, ( SELECT * FROM t2 ) AS alias
WHERE EXISTS ( SELECT * FROM t2 WHERE b = c ) 
OR a <= 10;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	alias1	ALL	NULL	NULL	NULL	NULL	14	
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	20	Using join buffer (flat, BNL join)
3	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	20	Using where
#---------------
# SHOW EXPLAIN output:
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	alias1	ALL	NULL	NULL	NULL	NULL	14	
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	20	Using join buffer (flat, BNL join)
3	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	20	

revision-id: psergey@askmonty.org-20120727121752-5dmlp1nkhrn01ab5
date: 2012-07-27 16:17:52 +0400
build-date: 2012-08-01 17:33:14 +0300
revno: 3460

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

CREATE TABLE t1 (a INT) ENGINE=MyISAM;
INSERT INTO t1 VALUES (7),(0),(9),(3),(4),(2),(5),(7),(0),(9),(3),(4),(2),(5);		

CREATE TABLE t2 (b INT, c INT) ENGINE=MyISAM;
INSERT INTO t2 VALUES 
(0,4),(8,6),(1,3),(8,5),(9,3),(24,246),(6,2),(1,9),(6,3),(2,8),
(4,1),(8,8),(4,8),(4,5),(7,7),(4,5),(1,1),(9,6),(4,2),(8,9);


let $query =
SELECT * 
FROM t1 AS alias1, ( SELECT * FROM t2 ) AS alias
WHERE EXISTS ( SELECT * FROM t2 WHERE b = c ) 
OR a <= 10;


eval EXPLAIN $query;
--echo #---------------
--echo # SHOW EXPLAIN output:

--connect (con1,localhost,root,,)
--let $con_id = `SELECT CONNECTION_ID()`

--let $trials = 50

--disable_query_log

while ($trials)
{
  --dec $trials
  --let $run = 1000

  --send_eval $query

  --connection default
  while ($run)
  {
    --error 0,1932
    eval SHOW EXPLAIN FOR $con_id;
    --dec $run
    if (!$mysql_errno)
    {
      --let $run = 0
      --let $trials = 0
      --let $found = 1
    }
  }

  --disable_result_log
  --connection con1
  --reap
  --enable_result_log

}

if (!$found)
{
  --echo ########### Could not catch the query by SHOW EXPLAIN, try again  #############
}

DROP TABLE t1, t2;