mysql 創建兩張表 建立關聯 外鍵

創建數據庫

mysql> create database lesson53;
Query OK, 1 row affected (0.01 sec)

 

創建第一張表

CREATE TABLE lesson53.ClassCharger(

       id TINYINT PRIMARY KEY auto_increment,
       name VARCHAR (20),
       age INT ,
       is_marriged boolean  -- show create table ClassCharger: tinyint(1)

);

給第一張表添加數據

mysql> INSERT INTO ClassCharger (name,age,is_marriged) VALUES ("冰冰",12,0),
    ->                                                        ("丹丹",14,0),
    ->                                                        ("歪歪",22,0),
    ->                                                        ("姍姍",20,0),
    ->                                                        ("小雨",21,0);

創建第二張表

mysql> CREATE TABLE Student2(
    ->        id INT PRIMARY KEY auto_increment,
    ->        name VARCHAR (20),
    ->        charger_id TINYINT,
    ->        CONSTRAINT charger_id FOREIGN KEY (charger_id) REFERENCES ClassCharger(id)
    -> );

     -- constraint 外鍵名稱 foreign key (外鍵名稱) references 主表名稱(主表列名稱)
     --切記:作為外鍵一定要和關聯主鍵的數據類型保持一致

Query OK, 0 rows affected (0.11 sec)

 

增加外鍵和刪除外鍵

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

ALTER TABLE student DROP FOREIGN KEY abc;