利用子查询，求出 MySQL 员工表中的最大和第二大工资？

使用子查询可以从员工表中获得最大和第二大工资。

首先让我们创建一个表。创建表的查询如下 -

mysql> create table EmployeeMaxAndSecondMaxSalary
   -> (
   -> EmployeeId int,
   -> Employeename varchar(20),
   -> EmployeeSalary int
   -> );
Query OK, 0 rows affected (0.88 sec)

使用 insert 命令在表中插入一些记录 -

mysql> insert into EmployeeMaxAndSecondMaxSalary values(1,'John',34566);
Query OK, 1 row affected (0.20 sec)

mysql> insert into EmployeeMaxAndSecondMaxSalary values(2,'Bob',56789);
Query OK, 1 row affected (0.17 sec)

mysql> insert into EmployeeMaxAndSecondMaxSalary values(3,'Carol',44560);
Query OK, 1 row affected (0.26 sec)

mysql> insert into EmployeeMaxAndSecondMaxSalary values(4,'Sam',76456);
Query OK, 1 row affected (0.29 sec)

mysql> insert into EmployeeMaxAndSecondMaxSalary values(5,'Mike',65566);
Query OK, 1 row affected (0.14 sec)

mysql> insert into EmployeeMaxAndSecondMaxSalary values(6,'David',89990);
Query OK, 1 row affected (0.19 sec)

mysql> insert into EmployeeMaxAndSecondMaxSalary values(7,'James',68789);
Query OK, 1 row affected (0.12 sec)

mysql> insert into EmployeeMaxAndSecondMaxSalary values(8,'Robert',76543);
Query OK, 1 row affected (0.13 sec)

使用 select 语句显示表中的所有记录。查询如下 -

mysql> select *from EmployeeMaxAndSecondMaxSalary;

以下为输出。

+------------+--------------+----------------+
| EmployeeId | Employeename | EmployeeSalary |
+------------+--------------+----------------+
|          1 | John         |          34566 |
|          2 | Bob          |          56789 |
|          3 | Carol        |          44560 |
|          4 | Sam          |          76456 |
|          5 | Mike         |          65566 |
|          6 | David        |          89990 |
|          7 | James        |          68789 |
|          8 | Robert       |          76543 |
+------------+--------------+----------------+
8 rows in set (0.00 sec)

使用子查询获取最大和第二大工资的查询 -

mysql> select (select max(EmployeeSalary) from EmployeeMaxAndSecondMaxSalary) MaximumSalary,
   -> (select max(EmployeeSalary) from EmployeeMaxAndSecondMaxSalary
   -> where EmployeeSalary not in(select max(EmployeeSalary) from
EmployeeMaxAndSecondMaxSalary)) as SecondMaximumSalary;

以下输出显示了两项最高工资 -

+---------------+---------------------+
| MaximumSalary | SecondMaximumSalary |
+---------------+---------------------+
|         89990 |               76543 |
+---------------+---------------------+
1 row in set (0.00 sec)

更新于: 2019 年 7 月 30 日

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