更新了部分文档
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@ -159,14 +159,14 @@ select * from (
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) `temp` where `rank` between 4 and 6;
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```
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> **说明**:上面使用的函数`row_number()`可以为每条记录生成一个行号,在实际工作中可以根据需要将其替换为`rank()`或`dense_rank()`函数,三者的区别可以参考官方文档或阅读[《通俗易懂的学会:SQL窗口函数》](https://zhuanlan.zhihu.com/p/92654574)进行了解。在MySQL 8以前的版本,我们可以通过下面的方式来完成类似的操作。
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>
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> ```SQL
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> select `rank`, `ename`, `sal` from (
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> select @a:=@a+1 as `rank`, `ename`, `sal`
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> from `tb_emp`, (select @a:=0) as t1 order by `sal` desc
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> ) as `temp` where `rank` between 4 and 6;
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> ```
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上面使用的函数`row_number()`可以为每条记录生成一个行号,在实际工作中可以根据需要将其替换为`rank()`或`dense_rank()`函数,三者的区别可以参考官方文档或阅读[《通俗易懂的学会:SQL窗口函数》](https://zhuanlan.zhihu.com/p/92654574)进行了解。在MySQL 8以前的版本,我们可以通过下面的方式来完成类似的操作。
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```SQL
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select `rank`, `ename`, `sal` from (
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select @a:=@a+1 as `rank`, `ename`, `sal`
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from `tb_emp`, (select @a:=0) as t1 order by `sal` desc
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) as `temp` where `rank` between 4 and 6;
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```
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例子2:查询每个部门月薪最高的两名的员工的姓名和部门名称。
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@ -180,13 +180,13 @@ from (
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) as `temp` natural join `tb_dept` where `rank`<=2;
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```
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> 说明:在MySQL 8以前的版本,我们可以通过下面的方式来完成类似的操作。
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>
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> ```SQL
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> select `ename`, `sal`, `dname` from `tb_emp` as `t1`
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说明:在MySQL 8以前的版本,我们可以通过下面的方式来完成类似的操作。
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```SQL
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select `ename`, `sal`, `dname` from `tb_emp` as `t1`
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natural join `tb_dept`
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where (
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select count(*) from `tb_emp` as `t2`
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where `t1`.`dno`=`t2`.`dno` and `t2`.`sal`>`t1`.`sal`
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)<2 order by `dno` asc, `sal` desc;
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> ```
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```
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