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Mar 24, 2020 Replied to a topic by gssong › MySQL › abc 联合索引查 bc 走不走索引 |
@ahsjs == 见谅，先在 mysql 里跑的后敲在这的，没复制
Mar 24, 2020 Replied to a topic by gssong › MySQL › abc 联合索引查 bc 走不走索引 |
explain 一把试试。
1. 用的 mysql 5.6.40 ，innodb
2. create table abcd (a varchar(255), b varchar(255), c varchar(255), d varcahr(255));
3. alter table abcd add index abc(a,b,c);
4. explain select a,b from abcd; # using index
5. explain select b,c from abcd; # using index
6. explain select c,d from abcd; # null
1. 用的 mysql 5.6.40 ，innodb
2. create table abcd (a varchar(255), b varchar(255), c varchar(255), d varcahr(255));
3. alter table abcd add index abc(a,b,c);
4. explain select a,b from abcd; # using index
5. explain select b,c from abcd; # using index
6. explain select c,d from abcd; # null
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