subselect.test

这是linux下运行的mysql软件包,可用于linux 下安装 php + mysql + apach 的网络配置

SELECT a FROM t1 WHERE a <> ANY ( SELECT a FROM t1 WHERE b = 2 );
SELECT a FROM t1 WHERE a > ALL ( SELECT a FROM t1 WHERE b = 2 );
SELECT a FROM t1 WHERE a < ALL ( SELECT a FROM t1 WHERE b = 2 );
SELECT a FROM t1 WHERE a = ALL ( SELECT a FROM t1 WHERE b = 2 );
SELECT a FROM t1 WHERE a >= ALL ( SELECT a FROM t1 WHERE b = 2 );
SELECT a FROM t1 WHERE a <= ALL ( SELECT a FROM t1 WHERE b = 2 );
SELECT a FROM t1 WHERE a <> ALL ( SELECT a FROM t1 WHERE b = 2 );
# having clause test
SELECT a FROM t1 WHERE a > ANY (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a < ANY (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a = ANY (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a >= ANY (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <= ANY (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <> ANY (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a > ALL (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a < ALL (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a = ALL (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a >= ALL (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <= ALL (SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <> ALL (SELECT a FROM t1 HAVING a = 2);
# union test
SELECT a FROM t1 WHERE a > ANY (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a < ANY (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a = ANY (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a >= ANY (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a <= ANY (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a <> ANY (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a > ALL (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a < ALL (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a = ALL (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a >= ALL (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a <= ALL (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE a <> ALL (SELECT a FROM t1 WHERE b = 2 UNION SELECT a FROM t1 WHERE b = 2);
# union + having test
SELECT a FROM t1 WHERE a > ANY (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a < ANY (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a = ANY (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a >= ANY (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <= ANY (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <> ANY (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a > ALL (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a < ALL (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a = ALL (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a >= ALL (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <= ALL (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE a <> ALL (SELECT a FROM t1 HAVING a = 2 UNION SELECT a FROM t1 HAVING a = 2);
# row tests
# < > >= <= and = ALL/ <> ANY do not support row operation
-- error 1241
SELECT a FROM t1 WHERE (1,2) > ANY (SELECT a FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE a > ANY (SELECT a,2 FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE (1,2) > ANY (SELECT a,2 FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE (1,2) > ALL (SELECT a FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE a > ALL (SELECT a,2 FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE (1,2) > ALL (SELECT a,2 FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE (1,2) = ALL (SELECT a,2 FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE (1,2) <> ANY (SELECT a,2 FROM t1 WHERE b = 2);
# following should be converted to IN
-- error 1241
SELECT a FROM t1 WHERE (1,2) = ANY (SELECT a FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE a = ANY (SELECT a,2 FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE (1,2) = ANY (SELECT a,2 FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE (1,2) <> ALL (SELECT a FROM t1 WHERE b = 2);
-- error 1241
SELECT a FROM t1 WHERE a <> ALL (SELECT a,2 FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE (1,2) <> ALL (SELECT a,2 FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE (a,1) = ANY (SELECT a,1 FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE (a,1) <> ALL (SELECT a,1 FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE (a,1) = ANY (SELECT a,1 FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE (a,1) <> ALL (SELECT a,1 FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE (a,1) = ANY (SELECT a,1 FROM t1 WHERE b = 2 UNION SELECT a,1 FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE (a,1) <> ALL (SELECT a,1 FROM t1 WHERE b = 2 UNION SELECT a,1 FROM t1 WHERE b = 2);
SELECT a FROM t1 WHERE (a,1) = ANY (SELECT a,1 FROM t1 HAVING a = 2 UNION SELECT a,1 FROM t1 HAVING a = 2);
SELECT a FROM t1 WHERE (a,1) <> ALL (SELECT a,1 FROM t1 HAVING a = 2 UNION SELECT a,1 FROM t1 HAVING a = 2);
# without optimisation
SELECT a FROM t1 WHERE a > ANY (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a < ANY (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a = ANY (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a >= ANY (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a <= ANY (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a <> ANY (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a > ALL (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a < ALL (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a = ALL (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a >= ALL (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a <= ALL (SELECT a FROM t1 WHERE b = 2 group by a);
SELECT a FROM t1 WHERE a <> ALL (SELECT a FROM t1 WHERE b = 2 group by a);
# without optimisation + having
SELECT a FROM t1 WHERE a > ANY (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a < ANY (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a = ANY (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a >= ANY (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a <= ANY (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a <> ANY (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a > ALL (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a < ALL (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a = ALL (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a >= ALL (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a <= ALL (SELECT a FROM t1 group by a HAVING a = 2);
SELECT a FROM t1 WHERE a <> ALL (SELECT a FROM t1 group by a HAVING a = 2);
# EXISTS in string contence
SELECT concat(EXISTS(SELECT a FROM t1 WHERE b = 2 and a.a > t1.a), '-') from t1 a;
SELECT concat(EXISTS(SELECT a FROM t1 WHERE b = 2 and a.a < t1.a), '-') from t1 a;
SELECT concat(EXISTS(SELECT a FROM t1 WHERE b = 2 and a.a = t1.a), '-') from t1 a;
DROP TABLE t1;
CREATE TABLE t1 ( a double, b double );
INSERT INTO t1 VALUES (1,1),(2,2),(3,3);
SELECT a FROM t1 WHERE a > ANY (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a < ANY (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a = ANY (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a >= ANY (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a <= ANY (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a <> ANY (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a > ALL (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a < ALL (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a = ALL (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a >= ALL (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a <= ALL (SELECT a FROM t1 WHERE b = 2e0);
SELECT a FROM t1 WHERE a <> ALL (SELECT a FROM t1 WHERE b = 2e0);
DROP TABLE t1;
CREATE TABLE t1 ( a char(1), b char(1));
INSERT INTO t1 VALUES ('1','1'),('2','2'),('3','3');
SELECT a FROM t1 WHERE a > ANY (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a < ANY (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a = ANY (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a >= ANY (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a <= ANY (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a <> ANY (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a > ALL (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a < ALL (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a = ALL (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a >= ALL (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a <= ALL (SELECT a FROM t1 WHERE b = '2');
SELECT a FROM t1 WHERE a <> ALL (SELECT a FROM t1 WHERE b = '2');
DROP TABLE t1;


#
# SELECT(EXISTS * ...)optimisation
#
create table t1 (a int, b int);
insert into t1 values (1,2),(3,4);
select * from t1 up where exists (select * from t1 where t1.a=up.a);
explain extended select * from t1 up where exists (select * from t1 where t1.a=up.a);
drop table t1;

#
# Bug #4102: subselect in HAVING
#

CREATE TABLE t1 (t1_a int);
INSERT INTO t1 VALUES (1);
CREATE TABLE t2 (t2_a int, t2_b int, PRIMARY KEY (t2_a, t2_b));
INSERT INTO t2 VALUES (1, 1), (1, 2);
SELECT * FROM t1, t2 table2 WHERE t1_a = 1 AND table2.t2_a = 1
  HAVING table2.t2_b = (SELECT MAX(t2_b) FROM t2 WHERE t2_a = table2.t2_a);
DROP TABLE t1, t2;

#
# Test problem with NULL and derived tables (Bug #4097)
#

CREATE TABLE t1 (id int(11) default NULL,name varchar(10) default NULL);
INSERT INTO t1 VALUES (1,'Tim'),(2,'Rebecca'),(3,NULL);
CREATE TABLE t2 (id int(11) default NULL, pet varchar(10) default NULL);
INSERT INTO t2 VALUES (1,'Fido'),(2,'Spot'),(3,'Felix');
SELECT a.*, b.* FROM (SELECT * FROM t1) AS a JOIN t2 as b on a.id=b.id;
drop table t1,t2;

#
# outer fields resolving in INSERT/REPLACE and CRETE with SELECT
#
CREATE TABLE t1 ( a int, b int );
CREATE TABLE t2 ( c int, d int );
INSERT INTO t1 VALUES (1,2), (2,3), (3,4);
SELECT a AS abc, b FROM t1 WHERE b = (SELECT MIN(b) FROM t1 WHERE a=abc);
INSERT INTO t2 SELECT a AS abc, b FROM t1 WHERE b = (SELECT MIN(b) FROM t1 WHERE a=abc);
select * from t2;
CREATE TABLE t3 SELECT a AS abc, b FROM t1 WHERE b = (SELECT MIN(b) FROM t1 WHERE a=abc);
select * from t3;
prepare stmt1 from "INSERT INTO t2 SELECT a AS abc, b FROM t1 WHERE b = (SELECT MIN(b) FROM t1 WHERE a=abc);";
execute stmt1;
deallocate prepare stmt1;
select * from t2;
drop table t3;
prepare stmt1 from "CREATE TABLE t3 SELECT a AS abc, b FROM t1 WHERE b = (SELECT MIN(b) FROM t1 WHERE a=abc);";
execute stmt1;
select * from t3;
deallocate prepare stmt1;
DROP TABLE t1, t2, t3;

#
# Aggregate function comparation with ALL/ANY/SOME subselect
#
CREATE TABLE `t1` ( `a` int(11) default NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1;
insert into t1 values (1);
CREATE TABLE `t2` ( `b` int(11) default NULL, `a` int(11) default NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1;
insert into t2 values (1,2);
select t000.a, count(*) `C` FROM t1 t000 GROUP BY t000.a HAVING count(*) > ALL (SELECT count(*) FROM t2 t001 WHERE t001.a=1);
drop table t1,t2;

#
# BUG#4769 - fulltext in subselect
#
create table t1 (a int not null auto_increment primary key, b varchar(40), fulltext(b)); 
insert into t1 (b) values ('ball'),('ball games'), ('games'), ('foo'), ('foobar'), ('Serg'), ('Sergei'),('Georg'), ('Patrik'),('Hakan'); 
create table t2 (a int); 
insert into t2 values (1),(3),(2),(7); 
select a,b from t1 where match(b) against ('Ball') > 0; 
select a from t2 where a in (select a from t1 where match(b) against ('Ball') > 0); 
drop table t1,t2;

#
# BUG#5003 - like in subselect
#
CREATE TABLE t1(`IZAVORGANG_ID` VARCHAR(11) CHARACTER SET latin1 COLLATE latin1_bin,`KUERZEL` VARCHAR(10) CHARACTER SET latin1 COLLATE latin1_bin,`IZAANALYSEART_ID` VARCHAR(11) CHARACTER SET latin1 COLLATE latin1_bin,`IZAPMKZ_ID` VARCHAR(11) CHARACTER SET latin1 COLLATE latin1_bin);
CREATE INDEX AK01IZAVORGANG ON t1(izaAnalyseart_id,Kuerzel);
INSERT INTO t1(`IZAVORGANG_ID`,`KUERZEL`,`IZAANALYSEART_ID`,`IZAPMKZ_ID`)VALUES('D0000000001','601','D0000000001','I0000000001');
INSERT INTO t1(`IZAVORGANG_ID`,`KUERZEL`,`IZAANALYSEART_ID`,`IZAPMKZ_ID`)VALUES('D0000000002','602','D0000000001','I0000000001');
INSERT INTO t1(`IZAVORGANG_ID`,`KUERZEL`,`IZAANALYSEART_ID`,`IZAPMKZ_ID`)VALUES('D0000000003','603','D0000000001','I0000000001');
INSERT INTO t1(`IZAVORGANG_ID`,`KUERZEL`,`IZAANALYSEART_ID`,`IZAPMKZ_ID`)VALUES('D0000000004','101','D0000000001','I0000000001');
SELECT `IZAVORGANG_ID` FROM t1 WHERE `KUERZEL` IN(SELECT MIN(`KUERZEL`)`Feld1` FROM t1 WHERE `KUERZEL` LIKE'601%'And`IZAANALYSEART_ID`='D0000000001');
drop table t1;

#
# Optimized IN with compound index
#
CREATE TABLE `t1` ( `aid` int(11) NOT NULL default '0', `bid` int(11) NOT NULL default '0', PRIMARY KEY  (`aid`,`bid`));
CREATE TABLE `t2` ( `aid` int(11) NOT NULL default '0', `bid` int(11) NOT NULL default '0', PRIMARY KEY  (`aid`,`bid`));
insert into t1 values (1,1),(1,2),(2,1),(2,2);
insert into t2 values (1,2),(2,2);
select * from t1 where t1.aid not in (select aid from t2 where bid=t1.bid);
alter table t2 drop primary key;
alter table t2 add key KEY1 (aid, bid);
select * from t1 where t1.aid not in (select aid from t2 where bid=t1.bid);
alter table t2 drop key KEY1;
alter table t2 add primary key (bid, aid);
select * from t1 where t1.aid not in (select aid from t2 where bid=t1.bid);
drop table t1,t2;

#
# resolving fields of grouped outer SELECT
#
CREATE TABLE t1 (howmanyvalues bigint, avalue int);
INSERT INTO t1 VALUES (1, 1),(2, 1),(2, 2),(3, 1),(3, 2),(3, 3),(4, 1),(4, 2),(4, 3),(4, 4);
SELECT howmanyvalues, count(*) from t1 group by howmanyvalues;
SELECT a.howmanyvalues, (SELECT count(*) from t1 b where b.howmanyvalues = a.howmanyvalues) as mycount from t1 a group by a.howmanyvalues;
CREATE INDEX t1_howmanyvalues_idx ON t1 (howmanyvalues);
SELECT a.howmanyvalues, (SELECT count(*) from t1 b where b.howmanyvalues+1 = a.howmanyvalues+1) as mycount from t1 a group by a.howmanyvalues;
SELECT a.howmanyvalues, (SELECT count(*) from t1 b where b.howmanyvalues = a.howmanyvalues) as mycount from t1 a group by a.howmanyvalues;
SELECT a.howmanyvalues, (SELECT count(*) from t1 b where b.howmanyvalues = a.avalue) as mycount from t1 a group by a.howmanyvalues;
drop table t1;

create table t1 (x int);
select  (select b.x from t1 as b where b.x=a.x) from t1 as a where a.x=2 group by a.x;
drop table t1;

#
# Test of correct maybe_null flag returning by subquwery for temporary table
# creation
#
CREATE TABLE `t1` ( `master` int(10) unsigned NOT NULL default '0', `map` smallint(6) unsigned NOT NULL default '0', `slave` int(10) unsigned NOT NULL default '0', `access` int(10) unsigned NOT NULL default '0', UNIQUE KEY `access_u` (`master`,`map`,`slave`));
INSERT INTO `t1` VALUES (1,0,0,700),(1,1,1,400),(1,5,5,400),(1,12,12,400),(1,12,32,400),(4,12,32,400);
CREATE TABLE `t2` ( `id` int(10) unsigned NOT NULL default '0', `pid` int(10) unsigned NOT NULL default '0', `map` smallint(6) unsigned NOT NULL default '0', `level` tinyint(4) unsigned NOT NULL default '0', `title` varchar(255) default NULL, PRIMARY KEY  (`id`,`pid`,`map`), KEY `level` (`level`), KEY `id` (`id`,`map`)) ;
INSERT INTO `t2` VALUES (6,5,12,7,'a'),(12,0,0,7,'a'),(12,1,0,7,'a'),(12,5,5,7,'a'),(12,5,12,7,'a');
-- error 1054
SELECT b.sc FROM (SELECT (SELECT a.access FROM t1 a WHERE a.map = op.map AND a.slave = op.pid AND a.master = 1) ac FROM t2 op WHERE op.id = 12 AND op.map = 0) b;
SELECT b.ac FROM (SELECT (SELECT a.access FROM t1 a WHERE a.map = op.map AND a.slave = op.pid AND a.master = 1) ac FROM t2 op WHERE op.id = 12 AND op.map = 0) b;
drop tables t1,t2;

#
# Test for bug #6462. "Same request on same data returns different
# results." a.k.a. "Proper cleanup of subqueries is missing for 
# SET and DO statements".
#
create table t1 (a int not null, b int not null, c int, primary key (a,b));
insert into t1 values (1,1,1), (2,2,2), (3,3,3);
set @b:= 0;
# Let us check that subquery will use covering index
explain select sum(a) from t1 where b > @b;
# This should not crash -debug serve