From 86689be24e8288bc34608b5cdf04ac5d45c3e4ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=90=B4=E4=BD=B3=E5=AE=87=2E?= <2541095587@qq.com>
Date: Wed, 25 Sep 2024 21:19:28 +0800
Subject: [PATCH] =?UTF-8?q?20240924=E4=BD=9C=E4=B8=9A?=
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+# 一，笔记
+
+1. #### 创建无参存储过程
+
+   1. ```sql
+      delimiter 设置新分隔符
+      create procedure 存储过程名()
+      begin
+      sql语句集;
+      end 新分割符
+      delimiter ;(还原分隔符)
+      ```
+
+2. ####  创建有参存储过程
+
+   1. ```sql
+      delimiter 设置新分隔符
+      create procedure 存储过程名(in 赋值变量名 数据类型(长度))
+      begin
+      select * from 表名 where 字段 = 赋值变量名;
+      ······
+      end 新分割符
+      delimiter ;(还原分隔符)
+      ```
+
+3.  #### 删除存储过程
+
+    1.  ```sql
+        drop procedure 存储过程名;
+        ```
+
+4.  #### 使用存储过程
+
+    1.  ```sql
+        call 存储过程名();
+        ```
+
+
+# 二、课堂练习
+
+1. #### 获取所有员工的姓名和薪水
+
+   ```sql
+   delimiter //
+   create procedure test1()
+   begin
+   select ename 员工姓名,sal 薪水 from emp where mgr is not null;
+   end//
+   delimiter ;
+   call test1();
+   ```
+
+2. #### 获取薪水最高的员工信息
+
+   ```sql
+   delimiter //
+   create procedure test2()
+   BEGIN
+   select * from emp where sal = (SELECT MAX(sal) from emp where mgr is not null);
+   end//
+   delimiter ;
+   ```
+
+3. #### 计算公司员工的平均薪水
+
+   ```sql
+   delimiter //
+   create procedure test3(out 员工平均薪水 decimal(10,5) )
+   BEGIN
+   select AVG(sal) into 员工平均薪水 from emp where mgr is not null;
+   select 员工平均薪水;
+   END //
+   delimiter ;
+   call test3(@sal);
+   ```
+
+4. #### 获取每个部门的员工数量
+
+   ```sql
+   delimiter //
+   create procedure test4()
+   begin 
+   select dname 部门名称,COUNT(empno) 员工数量 from dept d 
+   left join (select * from emp where mgr is not null) e on e.deptno = d.deptno
+   GROUP BY d.dname;
+   end //
+   delimiter ;
+   call test4();
+   ```
+
+5. #### 根据员工姓名（变量），查询其姓名，及所在部门的名称和工资，工资等级
+
+   ```sql
+   delimiter //
+   create procedure test5(in e_name varchar(20))
+   begin
+   select ename 姓名,dname 部门名称,sal 工资,grade 工资等级 from dept d 
+   join (select * from emp where mgr is not null) e on e.deptno = d.deptno
+   join salgrade s on e.sal BETWEEN s.losal and s.hisal
+   where ename = e_name;
+   end //
+   delimiter ; 
+   call test5('甘宁');
+   ```
+
+6.  #### 计算每个薪水等级的员工数量
+
+    ```sql
+    delimiter //
+    CREATE procedure test6()
+    BEGIN
+    select grade 薪水等级,count(empno) 员工数量 from salgrade s
+    INNER JOIn (select * from emp where mgr is not null) e on e.sal BETWEEN s.losal and s.hisal
+    GROUP BY s.grade;
+    end //
+    delimiter ;
+    call test6();
+    ```
+
+7. #### 列出所有部门及其对应的员工数量（包括空部门）
+
+   ```sql
+   delimiter //
+   create procedure test7()
+   begin 
+   select dname 部门名称,count(e.empno) 员工数量 from dept d 
+   LEFT JOIN (select * from emp where mgr is not null) e on e.deptno = d.deptno
+   GROUP BY d.dname;
+   end //
+   delimiter ;
+   call test7();
+   ```
+
+8. #### 以上用存储过程实现，请调用
+
+9. #### 删除第2个存储过程
+
+   ```sql
+   drop procedure test2;
+   ```
+
+# 三、课后作业，创建无参的存储过程，实现：
+
+#### 1.获取每个部门薪水最高的员工，显示员工编号，姓名，部门编号，薪水
+
+```sql
+delimiter //
+create procedure b_1()
+begin 
+select empno 员工编号,ename 姓名,e.deptno 部门编号,sal 薪水 
+from emp e 
+where sal IN (select max(sal) max_sal from emp where mgr is not null GROUP BY deptno) ORDER BY e.deptno;
+end //
+delimiter ;
+call b_1();
+```
+
+#### 2.找出没有员工的部门名称
+
+```sql
+delimiter //
+create procedure b_2()
+begin 
+select d.deptno,dname,empno,ename from dept d 
+LEFT JOIN emp e on e.deptno = d.deptno
+where empno is null;
+end //
+delimiter ;
+call b_2();
+```
+
+#### 3.创建一个存储过程，删除薪水低于薪水等级3的员工，并查询剩余员工数
+
+```sql
+delimiter //
+create procedure b_3()
+begin 
+DELETE from emp where sal < (select losal FROM salgrade where grade = 3) and mgr is not null;
+SELECT count(*) from emp where mgr is not null;
+end //
+delimiter ;
+call b_3();
+```
+
+#### 4.调用存储过程，检查并返回最高薪水和最低薪水的员工信息
+
+```sql
+delimiter //
+create procedure b_4()
+BEGIN
+select * from emp where sal = (select MAX(sal) from emp where mgr is not null);
+select * from emp where sal = (select Min(sal) from emp where mgr is not null);
+end //
+delimiter ;
+call b_4();
+```
+
+# 四、预习作业，（可利用参数或变量实现）
+
+#### 1.利用存储过程重置员工薪水，提升薪水低于20000的员工薪水，提升额为当前最低薪水值的一半。最终显示最新的员工信息表
+
+```sql
+delimiter //
+create procedure demo1(out min_sal decimal(8,2) )
+begin 
+select * from emp;
+select min(sal) / 2 into min_sal from emp;
+update emp set sal = sal + (select min_sal)  where sal < 20000;
+SELECT * from emp;
+end //
+delimiter ;
+call demo1(@sal);
+```
+
+#### 2.利用存储过程，将低于全公司平均薪资水平的员工薪水改成平均工资。
+
+```sql
+delimiter //
+create procedure demo2(out avgsal decimal(8,2))
+begin 
+SELECT * from emp;
+select avg(sal) into avgsal from emp where mgr is not null;
+update emp set sal = (select avgsal) where sal < (select avgsal);
+end //
+delimiter ;
+call demo2(@sal);
+```
-- 
Gitee