MYSQL进阶学习笔记三：MySQL流程控制语句！（视频序号：进阶_7-10)

 1 --7 流程控制语句之选择语句
 2 DELIMITER //
 3 CREATE PROCEDURE p_test7(IN age INT)
 4 BEGIN
 5     IF age >=18 THEN SELECT ‘成年人‘;
 6     ELSE SELECT ‘未成年人‘;
 7     END IF;
 8 END 
 9 //
10 
11 DELIMITER ;
12 SET @age =4;
13 CALL p_test7(@age);
14 
15 SELECT @age;
16 
17 
18 DELIMITER //
19 CREATE PROCEDURE p_test8(IN age INT)
20 BEGIN
21     IF age >=18 AND  age < 60 THEN SELECT ‘成年人‘;
22     ELSEIF age >= 60 THEN SELECT ‘老年人‘;
23     ELSE SELECT ‘未成年人‘;
24     END IF;
25 END 
26 //
27 
28 DELIMITER ;
29 SET @age =60;
30 CALL p_test8(@age);
31 
32 SELECT @age;

 1 --8 流程控制语句之选择语句CASE分支
 2 
 3 --默认数据(创建工资表）
 4 CREATE DATABASE mzjj;
 5 USE mzjj;
 6 
 7 CREATE TABLE salaries(
 8 emp_no INT KEY NOT NULL AUTO_INCREMENT,
 9 salary INT,
10 from_data DATE DEFAULT ‘2015-04-01‘,
11 to_data DATE DEFAULT ‘2015-05-01‘
12 )AUTO_INCREMENT=1001;
13 
14 
15 
16 
17 DELIMITER //
18 CREATE PROCEDURE p_addsalary(IN v_empno INT)
19 BEGIN
20     DECLARE addS int;
21     CASE v_empno
22     WHEN 1001 THEN SET addS = 1500;
23     WHEN 1002 THEN SET addS = 2500;
24     WHEN 1003 THEN SET addS = 3500;
25     ELSE SET adds =1000;
26     END CASE;
27     UPDATE salaries SET  salary = addS WHERE emp_no= v_empno;
28 END 
29 //
30 
31 DELIMITER ;
32 SET @v_empno =1001;
33 CALL p_addsalary(@v_empno);
34 
35 SELECT @v_empno;
36 
37 --默认数据(创建员工信息表）
38 CREATE TABLE employees(
39 emp_no INT KEY NOT NULL AUTO_INCREMENT,
40 birth_data DATE DEFAULT ‘2015-04-01‘,
41 first_name VARCHAR(20),
42 last_name VARCHAR(20),
43 gender ENUM(‘M‘,‘F‘),
44 hire_data DATE DEFAULT ‘2015-05-01‘
45 )AUTO_INCREMENT=1001;
46 
47 SELECT emp_no,first_name,last_name,
48 (CASE gender WHEN ‘M‘ THEN ‘男‘ELSE ‘女‘ END) AS ‘性别‘ FROM employees;

1 --测试IFNULL函数
2 UPDATE employees SET first_name=NULL WHERE emp_no =1001;
3 SELECT IFNULL(first_name,‘无名字‘) FROM employees;

 1 --9 流程控制（WHILE循环语句）
 2 --计算1加到100
 3 DELIMITER //
 4 CREATE PROCEDURE p_addnum()
 5 BEGIN
 6     DECLARE i int DEFAULT 1;
 7     DECLARE addresult int DEFAULT 0;
 8     WHILE i<= 100 DO
 9     SET addresult = addresult +i;
10     SET i = i+1;
11     END WHILE;
12     SELECT addresult;
13 END 
14 //
15 
16 DELIMITER ;
17 CALL p_addnum();
18 
19 --向表中加入1000条数据
20 DELIMITER //
21 CREATE PROCEDURE p_insertEmp()
22 BEGIN
23     DECLARE maxempno int DEFAULT 0;
24     DECLARE i int DEFAULT 1;
25     WHILE i<= 1000 DO
26     SELECT MAX(emp_no) into maxempno FROM employees;
27     SET maxempno = maxempno+1;
28     INSERT INTO employees(emp_no,birth_data, first_name,last_name, gender,hire_data)
29         VALUES(maxempno,‘1990-1-1‘,‘jim‘,‘ju‘,‘M‘,‘2000-1-1‘);
30     SET i =i+1;
31     END WHILE;
32 END 
33 //
34 
35 DELIMITER ;
36 CALL p_insertEmp();

 1 --任务作业
 2 --更新编号为偶数的gender字段为M
 3 
 4 DELIMITER //
 5 CREATE PROCEDURE changeEmp()
 6 BEGIN
 7 
 8     DECLARE maxempno int DEFAULT 0;
 9     DECLARE sex VARCHAR(2) DEFAULT ‘M‘;
10     DECLARE minempno int DEFAULT 1;
11     SELECT MAX(emp_no) into maxempno FROM employees;
12     SELECT MIN(emp_no) into minempno FROM employees;
13     WHILE minempno <= maxempno DO
14         CASE minempno%2 
15         WHEN 0 THEN SET sex = ‘M‘;
16         ELSE SET sex = ‘M‘;
17         END CASE;
18     UPDATE employees SET  gender = sex WHERE emp_no= minempno;
19     SET minempno =minempno+1 ;
20     END WHILE;
21 END 
22 //
23 DELIMITER ;
24 CALL changeEmp();
25 
26 SELECT * FROM employees;
27 
28 DELIMITER //
29 CREATE PROCEDURE changeEmp2()
30 BEGIN
31 
32     DECLARE maxempno int DEFAULT 0;
33     DECLARE minempno int DEFAULT 1;
34     SELECT MAX(emp_no) into maxempno FROM employees;
35     SELECT MIN(emp_no) into minempno FROM employees;
36     WHILE minempno <= maxempno DO
37         IF minempno%2=0  THEN UPDATE employees SET  gender = ‘F‘ WHERE emp_no= minempno;
38         END IF;
39     SET minempno =minempno+1 ;
40     END WHILE;
41 END 
42 //
43 DELIMITER ;
44 CALL changeEmp2();

 1 --rapeat测试
 2 DELIMITER //
 3 CREATE PROCEDURE changeEmp1()
 4 BEGIN
 5 
 6     DECLARE maxempno int DEFAULT 0;
 7     DECLARE sex VARCHAR(2) DEFAULT ‘M‘;
 8     DECLARE minempno int DEFAULT 1;
 9     SELECT MAX(emp_no) into maxempno FROM employees;
10     SELECT MIN(emp_no) into minempno FROM employees;
11     REPEAT
12         if minempno%2 =0 then update employees SET gender=‘F‘ WHERE emp_no = minempno;
13         END IF;
14         SET minempno = minempno+1;
15         UNTIL minempno>maxempno
16     END REPEAT;
17 END 
18 //
19 DELIMITER ;
20 CALL changeEmp1();

 1 --loop测试
 2 DELIMITER //
 3 CREATE PROCEDURE changeEmp3()
 4 
 5 BEGIN
 6     DECLARE maxempno int DEFAULT 0;
 7     DECLARE minempno int DEFAULT 1;
 8     SELECT MAX(emp_no) into maxempno FROM employees;
 9     SELECT MIN(emp_no) into minempno FROM employees;
10     
11     myloop:loop
12         if minempno%2 =1 then update employees SET hire_data=‘1900-12-11‘ WHERE emp_no = minempno;
13         END IF;
14         SET minempno = minempno+1;
15         IF minempno>maxempno THEN LEAVE myloop;
16         END IF;
17     END loop;
18 END 
19 //
20 
21 DELIMITER ;
22 CALL changeEmp3();