-- 創(chuàng)建被關(guān)聯(lián)表，部門(mén)表
mysql> create table bm(
    id int primary key auto_increment, 
    bm_name varchar(10), 
    bm_desc char(64)
);
Query OK, 0 rows affected (0.01 sec)

mysql> desc bm;
+---------+-------------+------+-----+---------+----------------+
| Field   | Type        | Null | Key | Default | Extra          |
+---------+-------------+------+-----+---------+----------------+
| id      | int(11)     | NO   | PRI | NULL    | auto_increment |
| bm_name | varchar(10) | YES  |     | NULL    |                |
| bm_desc | char(64)    | YES  |     | NULL    |                |
+---------+-------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)

-- 創(chuàng)建外鍵所在的表，員工表
mysql> create table yg(
    id int primary key auto_increment, 
    yg_name varchar(6), 
    bm_id int, 
    foreign key(bm_id) references bm(id)  -- 表示bm_id是外鍵字段，關(guān)聯(lián)到bm表中的id字段
    on update cascade  # 級(jí)聯(lián)更新
    on delete cascade  # 級(jí)聯(lián)刪除
);
Query OK, 0 rows affected (0.10 sec)

mysql> desc yg;
+---------+------------+------+-----+---------+----------------+
| Field   | Type       | Null | Key | Default | Extra          |
+---------+------------+------+-----+---------+----------------+
| id      | int(11)    | NO   | PRI | NULL    | auto_increment |
| yg_name | varchar(6) | YES  |     | NULL    |                |
| bm_id   | int(11)    | YES  | MUL | NULL    |                |
+---------+------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)


-- 插入數(shù)據(jù)
mysql> insert into bm (bm_name, bm_desc) values ('python', '人生苦短'),('go', 'let us go');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from bm;
+----+---------+--------------+
| id | bm_name | bm_desc      |
+----+---------+--------------+
|  1 | python  | 人生苦短     |
|  2 | go      | let us go    |
+----+---------+--------------+
2 rows in set (0.00 sec)


mysql> insert into yg (yg_name, bm_id) values ('xu', 1), ('zhuang', 2), ('lili', 1);
Query OK, 3 rows affected (0.09 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from yg;
+----+---------+-------+
| id | yg_name | bm_id |
+----+---------+-------+
|  2 | xu      |     1 |
|  3 | zhuang  |     2 |
|  4 | lili    |     1 |
+----+---------+-------+
3 rows in set (0.00 sec)

-- 外鍵關(guān)聯(lián)的數(shù)據(jù)必須在被關(guān)聯(lián)表中存在否則會(huì)報(bào)錯(cuò)哦~
mysql> insert into yg (yg_name, bm_id) values ('xu', 3);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`book_manage`.`yg`, CONSTRAINT `yg_ibfk_1` FOREIGN KEY (`bm_id`) REFERENCES `bm` (`id`))

-- 如果不使用級(jí)聯(lián)更新和刪除的話會(huì)出現(xiàn)下面的錯(cuò)誤，下述的SQL語(yǔ)句后面的文章都會(huì)介紹。。。
mysql> update bm set id=5 where id=2;  -- 將bm表中id=2的記錄改為id=5
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`book_manage`.`yg`, CONSTRAINT `yg_ibfk_1` FOREIGN KEY (`bm_id`) REFERENCES `bm` (`id`))

mysql> delete from bm where id =2;  -- 刪除bm表中id為2的那條記錄
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`book_manage`.`yg`, CONSTRAINT `yg_ibfk_1` FOREIGN KEY (`bm_id`) REFERENCES `bm` (`id`)) 

-- 創(chuàng)建書(shū)籍表
create table book(
    id int primary key auto_increment,
    title varchar(32),
    price int,
    author_id int,
    foreign key(author_id) references author(id)
    on update cascade
    on delete cascade
);

-- 創(chuàng)建作者表
create table author(
    id int primary key auto_increment,
    name varchar(32),
    age int,
    book_id int,
    foreign key(book_id) references book(id)
    on update cascade
    on delete cascade
);

-- 創(chuàng)建書(shū)籍表
mysql> create table book(
    id int primary key auto_increment, 
    name varchar(10), 
    price int
);
Query OK, 0 rows affected (0.01 sec)

-- 創(chuàng)建作者表
mysql> create table author(
    id int primary key auto_increment, 
    name varchar(6), 
    age int
);
Query OK, 0 rows affected (0.01 sec)


-- 創(chuàng)建第三章表，存儲(chǔ)book和author表的關(guān)聯(lián)關(guān)系
mysql> create table book2author(
    id int primary key auto_increment, 
    author_id int, 
    book_id int, 
    foreign key(author_id) references author(id) 
    on update cascade 
    on delete cascade, 	
    foreign key(book_id) references book(id) 
    on update cascade 
    on delete cascade);
Query OK, 0 rows affected (0.02 sec)

-- 創(chuàng)建用戶(hù)詳情表
create table authordetail(
	id int primary key auto_increment,
	phone int,
	addr varchar(64)
);

-- 用戶(hù)基本信息表
create table author(
	id int primary key auto_increment,
    name varchar(32),
    age int,
    authordetali_id int,
    foreign key(authordetali_id) references authordetali(id)
    on update cascade
    on delete cascade
);