外键:foreign key 一张表(A)中有一个字段,保存的值指向另外一张表(B)的主键 B:主表 A:从表 外键的操作 增加外键 Mysql中提供了两种方式增加外键 1、 方案1:在创建表的时候增加外键(类似主键) 基本语法:在字段之后增加一条语句 [constraint '外键名'] foreign key(外键字段) references 主表(主键); 1. ...
Experiment with the other tools on the vertical toolbar. Delete a relationship by selecting the eraser tool and clicking the line joining two tables. Create a view, add a text object, or add a layer. Save your changes to a MySQL Workbench model file (.mwbextension) by choosingSavefrom the...
PRIMARYKEY(`id`) ) ENGINE=InnoDBDEFAULTCHARSET=latin1; CREATETABLE`xiaodi` ( `id`int(11)NOTNULLauto_increment, `dage_id`int(11)defaultNULL, `name`varchar(32)default'', PRIMARYKEY(`id`), KEY`dage_id` (`dage_id`), CONSTRAINT`xiaodi_ibfk_1`FOREIGNKEY(`dage_id`)REFERENCES`dage` (`id...
create table repo_table( repo_id char(13) not null primary key, repo_name char(14) not null) type=innodb; 创建表2 mysql> create table busi_table( -> busi_id char(13) not null primary key, -> busi_name char(13) not null, -> repo_id char(13) not null, -> foreign key(repo_...
show create table emp; show create table emp; 1. 2. 运行效果如下: 其实我们在表的信息中也可以看到:(注意书写命令的格式) (2)删除外键: alter table emp drop foreign key 外键名; alter table emp drop foreign key 外键名; 1. 2. 二、表连接(join) ...
That's all you have to do to create aforeign key in MySQL, but because MySQL supports multiple database engines (database storage engines), you need to know if your foreign key declaration is really going to do what you think it will. ...
my problem is that after creating a foreign key, I cannot see in MySQL/phpMyAdmin that a column is a foreign key, here is an example of 2 tables (I wanted to create a table with users in a community an create a table=relationship which contains the information about which users know ea...
mysql> create table busi_table( -> busi_id char(13) not null primary key, -> busi_name char(13) not null, -> repo_id char(13) not null, -> foreign key(repo_id) references repo_table(repo_id)) -> type=innodb; 2)插入数据 ...
This following example relates parent and child tables through a single-column foreign key and shows how a foreign key constraint enforces referential integrity. Create the parent and child tables using the following SQL statements: CREATE TABLE parent ( id INT NOT NULL, PRIMARY KEY (id) ) ...
如果ctrl+s保存myorder表就会报错。 解决 修改myorder表中字段userId的值即可(与user表匹配) ctrl+s,不再报错 参考文章 Mysql错误1452 - Cannot add or update a child row: a foreign key constraint fails 原因及解决方法