mysql数据库建表、删表、设置外键、增删改查语句实例

-- 1、建表-----------------------------------------------
CREATE TABLE student (
	id INT  PRIMARY KEY AUTO_INCREMENT,
	NO INT,
	NAME VARCHAR(20) ,
	gender CHAR(1) ,
	gradeid INT ,
	phone INT  ,
	address VARCHAR(15) ,
	register_time DATETIME ,
	userid INT 
)
-- 2、删表-----------------------------------------------
DROP TABLE student

-- 3、 设置外建----------------------------------------------------------------
ALTER TABLE student ADD CONSTRAINT fk_student_userid FOREIGN KEY(userid) REFERENCES USER(id);
ALTER TABLE student ADD CONSTRAINT fk_student_gradeid FOREIGN KEY(gradeid) REFERENCES grade(id);

-- 4、选择查询------------------------------------------------
SELECT
	s.id,
	s.no,
	s.name sname,
	s.gender,
	g.name gname,
	s.phone,
	s.address,
	s.register_time,
	u.account
	  FROM student s LEFT JOIN grade g ON s.gradeid = g.id
			 LEFT JOIN USER u ON s.userid = u.id 

//选择------------------------------------------------------
SELECT * FROM student WHERE id = '1' 
//插入------------------------------------------------------
INSERT INTO student(NO,NAME,gender,gradeid,phone,address,register_time,userid)VALUE('107','马七','女',1,'555555555','大连','2021-01-08','2')
//删除------------------------------------------------------
DELETE FROM student WHERE id = '7' 
//修改------------------------------------------------------
UPDATE student SET NAME='jim',gender='男' WHERE id = 4

建表效果：