SELECT STRAIGHT_JOIN d.pla_id, m2.mat_id FROM t1 m2 INNER JOIN (SELECT mp.pla_id, MIN(m1.matintnum) AS matintnum FROM t2 mp INNER JOIN t1 m1 ON mp.mat_id=m1.mat_id GROUP BY mp.pla_id) d ON d.matintnum=m2.matintnum;
pla_id mat_id
102 1
101 1
100 1
104 2
103 2
105 3
SELECT STRAIGHT_JOIN d.pla_id, m2.test FROM t1 m2 INNER JOIN (SELECT mp.pla_id, MIN(m1.matintnum) AS matintnum FROM t2 mp INNER JOIN t1 m1 ON mp.mat_id=m1.mat_id GROUP BY mp.pla_id) d ON d.matintnum=m2.matintnum;
pla_id test
102 1
101 1
100 1
104 2
103 2
105 3
explain SELECT STRAIGHT_JOIN d.pla_id, m2.mat_id FROM t1 m2 INNER JOIN (SELECT mp.pla_id, MIN(m1.matintnum) AS matintnum FROM t2 mp INNER JOIN t1 m1 ON mp.mat_id=m1.mat_id GROUP BY mp.pla_id) d ON d.matintnum=m2.matintnum;
id select_type table type possible_keys key key_len ref rows Extra
explain SELECT STRAIGHT_JOIN d.pla_id, m2.test FROM t1 m2 INNER JOIN (SELECT mp.pla_id, MIN(m1.matintnum) AS matintnum FROM t2 mp INNER JOIN t1 m1 ON mp.mat_id=m1.mat_id GROUP BY mp.pla_id) d ON d.matintnum=m2.matintnum;
id select_type table type possible_keys key key_len ref rows Extra
create table t1 (E1 INTEGER UNSIGNED NOT NULL, E2 INTEGER UNSIGNED NOT NULL, E3 INTEGER UNSIGNED NOT NULL, PRIMARY KEY(E1)
);
insert into t1 VALUES(1,1,1), (2,2,1);
select count(*) from t1 INNER JOIN (SELECT A.E1, A.E2, A.E3 FROM t1 AS A WHERE A.E3 = (SELECT MAX(B.E3) FROM t1 AS B WHERE A.E2 = B.E2)) AS THEMAX ON t1.E1 = THEMAX.E2 AND t1.E1 = t1.E2;
count(*)
2
explain select count(*) from t1 INNER JOIN (SELECT A.E1, A.E2, A.E3 FROM t1 AS A WHERE A.E3 = (SELECT MAX(B.E3) FROM t1 AS B WHERE A.E2 = B.E2)) AS THEMAX ON t1.E1 = THEMAX.E2 AND t1.E1 = t1.E2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE A ALL NULL NULL NULL NULL 2 Using where
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.A.E2 1 Using where
3 DEPENDENT SUBQUERY B ALL NULL NULL NULL NULL 2 Using where
drop table t1;
create table t1 (a int);
insert into t1 values (1),(2);
select * from ( select * from t1 union select * from t1) a,(select * from t1 union select * from t1) b;
a a
1 1
2 1
1 2
2 2
explain select * from ( select * from t1 union select * from t1) a,(select * from t1 union select * from t1) b;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 4
1 PRIMARY <derived4> ALL NULL NULL NULL NULL 4 Using join buffer (flat, BNL join)
4 DERIVED t1 ALL NULL NULL NULL NULL 2
5 UNION t1 ALL NULL NULL NULL NULL 2
NULL UNION RESULT <union4,5> ALL NULL NULL NULL NULL NULL
2 DERIVED t1 ALL NULL NULL NULL NULL 2
3 UNION t1 ALL NULL NULL NULL NULL 2
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
drop table t1;
create table t2 (a int, b int, primary key (a));
insert into t2 values (1,7),(2,7);
explain select a from t2 where a>1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index PRIMARY PRIMARY 4 NULL 2 Using where; Using index
explain select a from (select a from t2 where a>1) tt;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index PRIMARY PRIMARY 4 NULL 2 Using where; Using index
set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
set @stmt= ' explain SELECT (SELECT SUM(c1 + c12 + 0.0) FROM t2 where (t1.c2 - 0e-3) = t2.c2 GROUP BY t1.c15 LIMIT 1) as scalar_s, exists (select 1.0e+0 from t2 where t2.c3 * 9.0000000000 = t1.c4) as exists_s, c5 * 4 in (select c6 + 0.3e+1 from t2) as in_s, (c7 - 4, c8 - 4) in (select c9 + 4.0, c10 + 40e-1 from t2) as in_row_s FROM t1, (select c25 x, c32 y from t2) tt WHERE x * 1 = c25 ' ;
prepare stmt1 from @stmt ;
execute stmt1 ;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
5 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
4 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
execute stmt1 ;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
5 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
4 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
explain SELECT (SELECT SUM(c1 + c12 + 0.0) FROM t2 where (t1.c2 - 0e-3) = t2.c2 GROUP BY t1.c15 LIMIT 1) as scalar_s, exists (select 1.0e+0 from t2 where t2.c3 * 9.0000000000 = t1.c4) as exists_s, c5 * 4 in (select c6 + 0.3e+1 from t2) as in_s, (c7 - 4, c8 - 4) in (select c9 + 4.0, c10 + 40e-1 from t2) as in_row_s FROM t1, (select c25 x, c32 y from t2) tt WHERE x * 1 = c25;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
5 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
4 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
deallocate prepare stmt1;
drop tables t1,t2;
set @@optimizer_switch=@save_optimizer_switch;
#
# LP bug #793436: query with a derived table for which optimizer proves
# that it contains not more than 1 row
#
CREATE TABLE t1 (a int, KEY (a)) ;
INSERT INTO t1 VALUES (3), (1);
CREATE TABLE t2 (a int);
INSERT INTO t2 VALUES (3);
EXPLAIN
SELECT * FROM (SELECT DISTINCT * FROM t2) t, t1 WHERE t1.a = t.a;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> system NULL NULL NULL NULL 1
1 PRIMARY t1 ref a a 5 const 1 Using index
2 DERIVED t2 system NULL NULL NULL NULL 1
SELECT * FROM (SELECT DISTINCT * FROM t2) t, t1 WHERE t1.a = t.a;
a a
3 3
DROP TABLE t1,t2;
#
# LP bug #800518: crash with a query over a derived table
# when a min/max optimization is applied
#
CREATE TABLE t1 (a int, b int, c varchar(10), INDEX idx(a,b)) ;