blob: 3e38a0d42183be5e5ea4147b498d677a115ab073 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
|
create table t1 (f1 char(4) primary key) engine=innodb charset=utf8 ;
insert into t1 values ('aaaa');
create table t2 (f2 text, f3 char(4) not null) engine=innodb charset=utf8 ;
create table t3 (id int not null) engine=innodb charset=utf8 ;
create table t4 (val int not null) engine=innodb charset=utf8;
explain select 1 from
(select f2, f3, val, count(id) from t4 join t2 left join t3 on 0) top
join t1 on f1 = f3 where f3 = 'aaaa' order by val;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 const PRIMARY PRIMARY 12 const 1 Using index
1 PRIMARY <derived2> ref key0 key0 13 const 0 Using where; Using filesort
2 DERIVED t4 ALL NULL NULL NULL NULL 1
2 DERIVED t2 ALL NULL NULL NULL NULL 1 Using join buffer (flat, BNL join)
2 DERIVED t3 ALL NULL NULL NULL NULL 1 Using where; Using join buffer (incremental, BNL join)
select 1 from
(select f2, f3, val, count(id) from t4 join t2 left join t3 on 0) top
join t1 on f1 = f3 where f3 = 'aaaa' order by val;
1
drop table t1, t2, t3, t4;
|
