记录

pycharm连接mysql出错：

删除一行：delete from classcharger where id=1；

，

修改表记录：update student2 set charger_id=4 where id=8 or id=9 or id=14;

，

 创建主表：

CREATE TABLE classcharger(id tinyint PRIMARY KEY auto_increment,
name VARCHAR (20),age INT ,is_married boolean);

INSERT INTO classcharger(name,age,is_married)VALUES ('bingbing',12,0),('dandan',14,0),('waiwai',20,0),('shanshan',20,0),('xiaoyu',21,0);
创建子表：

CREATE TABLE student2(id INT PRIMARY KEY auto_increment,
                      name VARCHAR (20),
                      charger_id tinyint,FOREIGN KEY (charger_id) REFERENCES classcharger(id)
                      ) engine=innodb;
INSERT INTO Student2(name,charger_id) VALUES ("alvin1",2),
                            ("alvin2",2),
                            ("alvin3",4),
                            ("alvin4",3),
                            ("alvin5",5),
                            ("alvin6",3),
                            ("alvin7",2);

-----------增加外键和删除外键---------

ALTER TABLE student  ADD CONSTRAINT abc
                     FOREIGN KEY(charger_id)
                     REFERENCES  classcharger(id);
ALTER TABLE student DROP FOREIGN KEY abc;