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19 lines
1,018 B
Text
19 lines
1,018 B
Text
create table t1 (f1 char(4) primary key) engine=innodb charset=utf8 ;
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insert into t1 values ('aaaa');
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create table t2 (f2 text, f3 char(4) not null) engine=innodb charset=utf8 ;
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create table t3 (id int not null) engine=innodb charset=utf8 ;
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create table t4 (val int not null) engine=innodb charset=utf8;
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explain select 1 from
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(select f2, f3, val, count(id) from t4 join t2 left join t3 on 0) top
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join t1 on f1 = f3 where f3 = 'aaaa' order by val;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1 const PRIMARY PRIMARY 12 const 1 Using index
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1 PRIMARY <derived2> ref key0 key0 13 const 0 Using where; Using filesort
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2 DERIVED t4 ALL NULL NULL NULL NULL 1
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2 DERIVED t2 ALL NULL NULL NULL NULL 1 Using join buffer (flat, BNL join)
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2 DERIVED t3 ALL NULL NULL NULL NULL 1 Using where; Using join buffer (incremental, BNL join)
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select 1 from
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(select f2, f3, val, count(id) from t4 join t2 left join t3 on 0) top
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join t1 on f1 = f3 where f3 = 'aaaa' order by val;
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1
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drop table t1, t2, t3, t4;
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