drop table if exists t1; create table t1 (id int not null, str char(10), unique(str)); explain select * from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 system NULL NULL NULL NULL 0 Const row not found insert into t1 values (1, null),(2, null),(3, "foo"),(4, "bar"); select * from t1 where str is null; id str 1 NULL 2 NULL select * from t1 where str="foo"; id str 3 foo explain select * from t1 where str is null; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref str str 11 const 2 Using index condition explain select * from t1 where str="foo"; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 const str str 11 const 1 explain select * from t1 ignore key (str) where str="foo"; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 4 Using where explain select * from t1 use key (str,str) where str="foo"; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 const str str 11 const 1 explain select * from t1 use key (str,str,foo) where str="foo"; ERROR 42000: Key 'foo' doesn't exist in table 't1' explain select * from t1 ignore key (str,str,foo) where str="foo"; ERROR 42000: Key 'foo' doesn't exist in table 't1' drop table t1; explain select 1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL No tables used create table t1 (a int not null); explain select count(*) from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away insert into t1 values(1); explain select count(*) from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away insert into t1 values(1); explain select count(*) from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away drop table t1; set names koi8r; create table таб (кол0 int, кол1 int, key инд0 (кол0), key инд01 (кол0,кол1)); insert into таб (кол0) values (1); insert into таб (кол0) values (2); explain select кол0 from таб where кол0=1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE таб ref инд0,инд01 инд0 5 const 1 Using index drop table таб; set names latin1; select 3 into @v1; explain select 3 into @v1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL No tables used create table t1(f1 int, f2 int); insert into t1 values (1,1); create view v1 as select * from t1 where f1=1; explain extended select * from v1 where f2=1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00 Warnings: Note 1003 select 1 AS `f1`,1 AS `f2` from dual where 1 explain extended select * from t1 where 0; id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE Warnings: Note 1003 select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f2` AS `f2` from `test`.`t1` where 0 explain extended select * from t1 where 1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00 Warnings: Note 1003 select 1 AS `f1`,1 AS `f2` from dual where 1 explain extended select * from t1 having 0; id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible HAVING Warnings: Note 1003 select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f2` AS `f2` from `test`.`t1` having 0 explain extended select * from t1 having 1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00 Warnings: Note 1003 select 1 AS `f1`,1 AS `f2` from dual having 1 drop view v1; drop table t1; CREATE TABLE t1(c INT); INSERT INTO t1 VALUES (),(); CREATE TABLE t2 (b INT, KEY(b),KEY(b),KEY(b),KEY(b),KEY(b), KEY(b),KEY(b),KEY(b),KEY(b),KEY(b), KEY(b),KEY(b),KEY(b),KEY(b),KEY(b), KEY(b),KEY(b),KEY(b),KEY(b),KEY(b), KEY(b),KEY(b),KEY(b),KEY(b),KEY(b), KEY(b),KEY(b),KEY(b),KEY(b),KEY(b), KEY(b),KEY(b),KEY(b),KEY(b),KEY(b), KEY(b),KEY(b),KEY(b),KEY(b),KEY(b)); Warnings: Note 1831 Duplicate index `b_2`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_3`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_4`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_5`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_6`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_7`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_8`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_9`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_10`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_11`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_12`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_13`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_14`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_15`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_16`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_17`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_18`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_19`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_20`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_21`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_22`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_23`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_24`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_25`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_26`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_27`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_28`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_29`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_30`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_31`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_32`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_33`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_34`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_35`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_36`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_37`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_38`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_39`. This is deprecated and will be disallowed in a future release Note 1831 Duplicate index `b_40`. This is deprecated and will be disallowed in a future release INSERT INTO t2 VALUES (),(),(); EXPLAIN SELECT 1 FROM (SELECT 1 FROM t2,t1 WHERE b < c GROUP BY 1 LIMIT 1) AS d2; id select_type table type possible_keys key key_len ref rows Extra X X X X X X X X X X X X X X X X X X X X X X X X X X X Range checked for each record (index map: 0xFFFFFFFFFF) DROP TABLE t2; DROP TABLE t1; CREATE TABLE t1(a INT); CREATE TABLE t2(a INT); INSERT INTO t1 VALUES (1),(2); INSERT INTO t2 VALUES (1),(2); EXPLAIN EXTENDED SELECT 1 FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY ALL NULL NULL NULL NULL 4 100.00 2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort 2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer (flat, BNL join) Warnings: Note 1003 /* select#1 */ select 1 AS `1` from (/* select#2 */ select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1` EXPLAIN EXTENDED SELECT 1 FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY ALL NULL NULL NULL NULL 4 100.00 2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort 2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer (flat, BNL join) Warnings: Note 1003 /* select#1 */ select 1 AS `1` from (/* select#2 */ select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1` prepare s1 from 'EXPLAIN EXTENDED SELECT 1 FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1'; execute s1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY ALL NULL NULL NULL NULL 4 100.00 2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort 2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer (flat, BNL join) Warnings: Note 1003 /* select#1 */ select 1 AS `1` from (/* select#2 */ select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1` prepare s1 from 'EXPLAIN EXTENDED SELECT 1 FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1'; execute s1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY ALL NULL NULL NULL NULL 4 100.00 2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort 2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer (flat, BNL join) Warnings: Note 1003 /* select#1 */ select 1 AS `1` from (/* select#2 */ select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1` execute s1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY ALL NULL NULL NULL NULL 4 100.00 2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort 2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer (flat, BNL join) Warnings: Note 1003 /* select#1 */ select 1 AS `1` from (/* select#2 */ select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1` DROP TABLE t1,t2; CREATE TABLE t1 (a INT PRIMARY KEY); EXPLAIN EXTENDED SELECT COUNT(a) FROM t1 USE KEY(a); ERROR 42000: Key 'a' doesn't exist in table 't1' DROP TABLE t1; CREATE TABLE t1(a LONGTEXT); INSERT INTO t1 VALUES (repeat('a',@@global.max_allowed_packet)); INSERT INTO t1 VALUES (repeat('b',@@global.max_allowed_packet)); EXPLAIN SELECT DISTINCT 1 FROM t1, (SELECT DISTINCTROW a AS away FROM t1 GROUP BY a WITH ROLLUP) as d1 WHERE t1.a = d1.a; ERROR 42S22: Unknown column 'd1.a' in 'where clause' DROP TABLE t1; # # Bug#48295: # explain extended crash with subquery and ONLY_FULL_GROUP_BY sql_mode # CREATE TABLE t1 (f1 INT not null); SELECT @@session.sql_mode INTO @old_sql_mode; SET SESSION sql_mode='ONLY_FULL_GROUP_BY'; EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE f1 > ALL( SELECT t.f1 FROM t1,t1 AS t ); id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables 2 SUBQUERY t1 system NULL NULL NULL NULL 0 0.00 Const row not found 2 SUBQUERY t system NULL NULL NULL NULL 0 0.00 Const row not found Warnings: Note 1003 /* select#1 */ select 1 AS `1` from `test`.`t1` where 0 SET SESSION sql_mode=@old_sql_mode; DROP TABLE t1; End of 5.0 tests. # # Bug#37870: Usage of uninitialized value caused failed assertion. # create table t1 (dt datetime not null, t time not null); create table t2 (dt datetime not null); insert into t1 values ('2001-01-01 1:1:1', '1:1:1'), ('2001-01-01 1:1:1', '1:1:1'); insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1'); SET @save_join_cache_level=@@join_cache_level; SET join_cache_level=0; flush tables; EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL ); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY OUTR ALL NULL NULL NULL NULL 2 Using where 1 PRIMARY INNR ALL NULL NULL NULL NULL 2 Using where; FirstMatch(OUTR) flush tables; SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL ); dt flush tables; EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' ); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY OUTR ALL NULL NULL NULL NULL 2 Using where 1 PRIMARY INNR ALL NULL NULL NULL NULL 2 Using where; FirstMatch(OUTR) flush tables; SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' ); dt 2001-01-01 01:01:01 2001-01-01 01:01:01 SET join_cache_level=@save_join_cache_level; drop tables t1, t2; # # Bug#47669: Query showed by EXPLAIN EXTENDED gives different result from original query # CREATE TABLE t1 (c int); INSERT INTO t1 VALUES (NULL); CREATE TABLE t2 (d int); INSERT INTO t2 VALUES (NULL), (0); EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY t1 system NULL NULL NULL NULL 1 100.00 2 SUBQUERY t2 ALL NULL NULL NULL NULL 2 100.00 Using where Warnings: Note 1276 Field or reference 'test.t1.c' of SELECT #2 was resolved in SELECT #1 Note 1003 /* select#1 */ select (/* select#2 */ select 1 from `test`.`t2` where `test`.`t2`.`d` = NULL) AS `(SELECT 1 FROM t2 WHERE d = c)` from dual DROP TABLE t1, t2; # # Bug#30302: Tables that were optimized away are printed in the # EXPLAIN EXTENDED warning. # create table t1(f1 int); create table t2(f2 int); insert into t1 values(1); insert into t2 values(1),(2); explain extended select * from t1 where f1=1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00 Warnings: Note 1003 select 1 AS `f1` from dual where 1 explain extended select * from t1 join t2 on f1=f2 where f1=1; id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00 1 SIMPLE t2 ALL NULL NULL NULL NULL 2 100.00 Using where Warnings: Note 1003 select 1 AS `f1`,`test`.`t2`.`f2` AS `f2` from `test`.`t2` where `test`.`t2`.`f2` = 1 drop table t1,t2; # # Bug #48419: another explain crash.. # CREATE TABLE t1 (a INT); CREATE TABLE t2 (b BLOB, KEY b(b(100))); INSERT INTO t2 VALUES ('1'), ('2'), ('3'); FLUSH TABLES; EXPLAIN SELECT 1 FROM t1 WHERE a = (SELECT 1 FROM t1 t JOIN t2 WHERE b <= 1 AND t.a); 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 2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL no matching row in const table DROP TABLE t1, t2; # # Bug #48573: difference of index selection between rpm binary and # .tar.gz, windows vs linux.. # CREATE TABLE t1(c1 INT, c2 INT, c4 INT, c5 INT, KEY(c2, c5), KEY(c2, c4, c5)); INSERT INTO t1 VALUES(4, 1, 1, 1); INSERT INTO t1 VALUES(3, 1, 1, 1); INSERT INTO t1 VALUES(2, 1, 1, 1); INSERT INTO t1 VALUES(1, 1, 1, 1); INSERT INTO t1 VALUES(5, 2, 1, 1); INSERT INTO t1 VALUES(6, 2, 1, 1); INSERT INTO t1 VALUES(7, 3, 1, 1); INSERT INTO t1 VALUES(9, 3, 1, 1); INSERT INTO t1 VALUES(10, 4, 1, 1); INSERT INTO t1 VALUES(11, 4, 1, 1); EXPLAIN SELECT c1 FROM t1 WHERE c2 = 1 AND c4 = 1 AND c5 = 1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref c2,c2_2 c2 10 const,const 4 Using where DROP TABLE t1; # # Bug#56814 Explain + subselect + fulltext crashes server # CREATE TABLE t1(f1 VARCHAR(6) NOT NULL, FULLTEXT KEY(f1),UNIQUE(f1)); INSERT INTO t1 VALUES ('test'); EXPLAIN SELECT 1 FROM t1 WHERE 1 > ALL((SELECT t1.f1 FROM t1 JOIN t1 a ON (MATCH(t1.f1) AGAINST ("")) WHERE t1.f1 GROUP BY t1.f1)); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t1 system NULL NULL NULL NULL 1 2 SUBQUERY a system NULL NULL NULL NULL 1 2 SUBQUERY t1 fulltext f1_2,f1 f1 0 1 Using where PREPARE stmt FROM 'EXPLAIN SELECT 1 FROM t1 WHERE 1 > ALL((SELECT t1.f1 FROM t1 RIGHT OUTER JOIN t1 a ON (MATCH(t1.f1) AGAINST ("")) WHERE t1.f1 GROUP BY t1.f1))'; EXECUTE stmt; id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t1 system NULL NULL NULL NULL 1 2 SUBQUERY a system NULL NULL NULL NULL 1 2 SUBQUERY t1 fulltext f1_2,f1 f1 0 1 Using where EXECUTE stmt; id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t1 system NULL NULL NULL NULL 1 2 SUBQUERY a system NULL NULL NULL NULL 1 2 SUBQUERY t1 fulltext f1_2,f1 f1 0 1 Using where DEALLOCATE PREPARE stmt; PREPARE stmt FROM 'EXPLAIN SELECT 1 FROM t1 WHERE 1 > ALL((SELECT t1.f1 FROM t1 JOIN t1 a ON (MATCH(t1.f1) AGAINST ("")) WHERE t1.f1 GROUP BY t1.f1))'; EXECUTE stmt; id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t1 system NULL NULL NULL NULL 1 2 SUBQUERY a system NULL NULL NULL NULL 1 2 SUBQUERY t1 fulltext f1_2,f1 f1 0 1 Using where EXECUTE stmt; id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t1 system NULL NULL NULL NULL 1 2 SUBQUERY a system NULL NULL NULL NULL 1 2 SUBQUERY t1 fulltext f1_2,f1 f1 0 1 Using where DEALLOCATE PREPARE stmt; DROP TABLE t1; End of 5.1 tests. # # Bug#11829785 EXPLAIN EXTENDED CRASH WITH RIGHT OUTER JOIN, SUBQUERIES # CREATE TABLE t1(a INT); INSERT INTO t1 VALUES (0), (0); PREPARE s FROM 'EXPLAIN EXTENDED SELECT SUBSTRING(1, (SELECT 1 FROM t1 a1 RIGHT OUTER JOIN t1 ON 0)) AS d FROM t1 WHERE 0 > ANY (SELECT @a FROM t1)'; EXECUTE s; ERROR 21000: Subquery returns more than 1 row DEALLOCATE PREPARE s; DROP TABLE t1; # # Bug#776295: EXPLAIN EXTENDED with always false multiple equality # in the WHERE condition of a derived table # CREATE TABLE t1 (a int) ; CREATE TABLE t2 (a int) ; INSERT INTO t2 VALUES (8); set @tmp_optimizer_switch=@@optimizer_switch; set optimizer_switch='derived_merge=off,derived_with_keys=off'; EXPLAIN EXTENDED SELECT * FROM ( SELECT t1.a FROM t1,t2 WHERE t2.a = t1.a ) AS t; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY system NULL NULL NULL NULL 0 0.00 Const row not found 2 DERIVED NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table Warnings: Note 1003 /* select#1 */ select NULL AS `a` from (/* select#2 */ select NULL AS `a` from `test`.`t1` where 0) `t` set optimizer_switch=@tmp_optimizer_switch; DROP TABLE t1,t2; # # MDEV-7215: EXPLAIN REPLACE produces an error: # Column count doesn't match value count # create table t1 (a int); insert into t1 values (1); create table t2 (b int, c int); replace into t2 select 100, (select a from t1); explain replace into t2 select 100, (select a from t1); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY NULL NULL NULL NULL NULL NULL NULL No tables used 2 SUBQUERY t1 system NULL NULL NULL NULL 1 drop table t1, t2; # End of 10.1 tests # # End of 10.2 test # # # MDEV-25564: Server crashed on running some EXPLAIN statements # EXPLAIN (SELECT 1,3) UNION (SELECT 2,1) ORDER BY (SELECT 2); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY NULL NULL NULL NULL NULL NULL NULL No tables used 2 UNION NULL NULL NULL NULL NULL NULL NULL No tables used NULL UNION RESULT ALL NULL NULL NULL NULL NULL Using filesort 3 SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used # # MDEV-23160: SIGSEGV in Explain_node::print_explain_for_children on UNION SELECT # CREATE TABLE t1 (a INT); INSERT INTO t1 VALUES (1),(2),(3); EXPLAIN SELECT * FROM t1 WHERE a IN (SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY (SELECT a)) UNION SELECT * FROM t1 ORDER BY (SELECT a); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t1 ALL NULL NULL NULL NULL 3 Using where 2 DEPENDENT SUBQUERY t1 ALL NULL NULL NULL NULL 3 Using where 3 DEPENDENT UNION t1 ALL NULL NULL NULL NULL 3 Using where NULL UNION RESULT ALL NULL NULL NULL NULL NULL 5 UNION t1 ALL NULL NULL NULL NULL 3 NULL UNION RESULT ALL NULL NULL NULL NULL NULL Using filesort 6 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used drop table t1; explain VALUES ( (VALUES (2))) UNION VALUES ( (SELECT 3)); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY NULL NULL NULL NULL NULL NULL NULL No tables used 5 SUBQUERY ALL NULL NULL NULL NULL 2 2 DERIVED NULL NULL NULL NULL NULL NULL NULL No tables used 3 UNION NULL NULL NULL NULL NULL NULL NULL No tables used NULL UNION RESULT ALL NULL NULL NULL NULL NULL Warnings: Note 1249 Select 4 was reduced during optimization