先创建三个表
CREATE TABLE clazz(
id INT NOT NULL PRIMARY KEY,
name VARCHAR(100) NOT NULL,
clazzroom VARCHAR(40) NOT NULL
);
CREATE TABLE group1(
id INT NOT NULL PRIMARY KEY ,
name VARCHAR(100) NOT NULL,
clazz_id INT NOT NULL,
foreign key(clazz_id) references clazz(id)
);
CREATE TABLE stu(
id INT NOT NULL PRIMARY KEY,
name VARCHAR(100) NOT NULL,
group_id INT NOT NULL,
foreign key(group_id) references group1(id)
);
通过外键把三个表联系起来
增删改查语句。
INSERT INTO table_name () VALUES ();
DELETE FROM table_name WHERE .....;
UPDATE table_name SET ··· WHERE ···;
SELECT * FROM table_name; 可以加where