学习笔记(14):MySQL数据库从入门到搞定实战-复合索引前导列特性

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未使用索引

select * from employee where salary=8800;

select * from employee where dept='部门A'；

select * from employee  where salary=8800 and dept='部门A';

使用索引

select * from employee where name='柳峰';

select * from employee where name='柳峰' and salary=8800;

select * from employee where name='柳峰' and salary=8800 and dept='部门A';