mysql流程函数

最新推荐文章于 2024-06-02 21:42:14 发布

原创最新推荐文章于 2024-06-02 21:42:14 发布 · 443 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#mysql #数据库

本文通过实例演示了MySQL中流程控制函数的使用，包括查询得分并根据得分展示不同等级评价，如优秀、良好、及格、不及格，以及对无成绩情况进行处理。详细展示了IF、IFNULL和CASE WHEN语句的应用。

use teaching;
-- 建表
-- 学生表
CREATE TABLE IF NOT EXISTS Student(
sid VARCHAR(20),
sname VARCHAR(20) NOT NULL DEFAULT '',
sbirth VARCHAR(20) NOT NULL DEFAULT '',
ssex VARCHAR(10) NOT NULL DEFAULT '',
PRIMARY KEY(sid)
);
-- 课程表
CREATE TABLE IF NOT EXISTS Course(
cid VARCHAR(20),
cname VARCHAR(20) NOT NULL DEFAULT '',
tid VARCHAR(20) NOT NULL,
PRIMARY KEY(cid)
);
-- 教师表
CREATE TABLE IF NOT EXISTS Teacher(
tid VARCHAR(20),
tname VARCHAR(20) NOT NULL DEFAULT '',
PRIMARY KEY(tid)
);
-- 成绩表
CREATE TABLE IF NOT EXISTS Sc(
sid VARCHAR(20),
cid VARCHAR(20),
score INT,
PRIMARY KEY(sid,cid)
);
-- 插入学生表测试数据
insert into Student values('01' , '赵雷' , '1990-01-01' , '男');
insert into Student values('02' , '钱电' , '1990-12-21' , '男');
insert into Student values('03' , '孙风' , '1990-05-20' , '男');
insert into Student values('04' , '李云' , '1990-08-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吴兰' , '1992-03-01' , '女');
insert into Student values('07' , '郑竹' , '1989-07-01' , '女');
insert into Student values('08' , '王菊' , '1990-01-20' , '女');
-- 课程表测试数据
insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');

-- 教师表测试数据
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');

-- 成绩表测试数据
insert into Sc values('01' , '01' , 80);
insert into Sc values('01' , '02' , 90);
insert into Sc values('01' , '03' , 99);
insert into Sc values('02' , '01' , 70);
insert into Sc values('02' , '02' , 60);
insert into Sc values('02' , '03' , 80);
insert into Sc values('03' , '01' , 80);
insert into Sc values('03' , '02' , 80);
insert into Sc values('03' , '03' , 80);
insert into Sc values('04' , '01' , 50);
insert into Sc values('04' , '02' , 30);
insert into Sc values('04' , '03' , 20);
insert into Sc values('05' , '01' , 76);
insert into Sc values('05' , '02' , 87);
insert into Sc values('06' , '01' , 31);
insert into Sc values('06' , '03' , 34);
insert into Sc values('07' , '02' , 89);
insert into Sc values('07' , '03' , 98);