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法律研究利用子查詢，求出 MySQL 員工表中的最大和第二大工資？
使用子查詢可以從員工表中獲得最大和第二大工資。
首先讓我們建立一個表。建立表的查詢如下 -
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記錄 -
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 語句顯示錶中的所有記錄。查詢如下 -
mysql> select *from EmployeeMaxAndSecondMaxSalary;
以下為輸出。
+------------+--------------+----------------+ | 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)
使用子查詢獲取最大和第二大工資的查詢 -
mysql> select (select max(EmployeeSalary) from EmployeeMaxAndSecondMaxSalary) MaximumSalary, -> (select max(EmployeeSalary) from EmployeeMaxAndSecondMaxSalary -> where EmployeeSalary not in(select max(EmployeeSalary) from EmployeeMaxAndSecondMaxSalary)) as SecondMaximumSalary;
以下輸出顯示了兩項最高工資 -
+---------------+---------------------+ | MaximumSalary | SecondMaximumSalary | +---------------+---------------------+ | 89990 | 76543 | +---------------+---------------------+ 1 row in set (0.00 sec)
更新於: 2019 年 7 月 30 日
193 次觀看
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