3.修改字段:ALTER TABLE 表名 CHANGE 原字段名 新字段名 数据类型[属性]; 4.删除字段:ALTER TABLE 表名 DROP 字段名; 2.添加主键 1.语法:ALTER TABLE 表名 ADD CONSTRAINT 主键名 PRIMARY KEY 表名(主键字段); 3.添加外键 1.语法:ALTER TABLE 表名 ADD CONNSTRAINT 外键名 FOREIGN KEY(外键字段) REFERE...
Based on the business requirements, an employee can only belong to one department. To make sure that the DepartmentID assigned to the employee exists in the [dbo].[Department] table, you create a FOREIGN KEY constraint on the column: ALTER TABLE [dbo].[Employee] ADD CONSTRAINT [FK_Employee...
altertabletbl_orderaddforeignkeyfk_user_id(user_id)referencesmgie_users(ID)onupdatecascadeondeleterestrict; 1. 2. 3. 4. 5. 错误 10:56:45 alter table tbl_order add foreign key fk_user_id(user_id) references mgie_users(ID) on update cascade on delete restrict Error Code: 1005. Can't ...
NOT NULL 约束只能通过ALTER TABLE modify 子句来添加 2、举个例子:给员工表中的manager_id列添加外键约束 alter TABLE s_emp ADD FOREIGN KEY(manager_id) references s_emp(id) 四、删除约束 ALTER TABLE 1、根据约束名来删除表中的指定约束 ALTER TABLE s_emp DROP CONSTRAINT s_emp_manager_id_fk; 2、...
外键约束名是你自己起的 比如你这个外键自己起名叫OK，那么这就写OK就行了 但是不能与库里现存的重复
CREATE TABLE `test2` ( `id` binary(16) NOT NULL, `description` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`) ); -- This command fails alter table test add constraint test_ri foreign key (main_contact) references test2; Does anyone know what is wrong?
Alter table 表名add foreign key(键名)reference 关联表(关联键名) Alter table 表名add Primary key(键名)reference 关联表(关联键名) Alter 表名add foreign key(键名)reference 关联键名) Alter 表名add Primary key(键名)reference 关联表(关联键名)相关...
如何在已经创建好的表上添加一个外键A.Alter table 表名 add foreign key(键名)reference 关联表(关联键名)B.Alter table 表名add Primary key(键名)reference 关联表(关联键名)C.Alter 表名add foreign key(键名)reference 关联键名)D.Alter 表名add Primary key(键名)reference 关联表(关联键名) 相关知识点:...
To Add a foreign key to a column in an existing table, use ALTER TABLE ADD CONSTRAINT [cc lang=”sql”] ALTER TABLE dbo.President_Lookup ADD CONSTRAINT fk_PresidentID FOREIGN KEY (PresidentID) REFERENCES dbo.Presidents (PresidentID) [/cc]...
ProcessOptionsUtilitiesHelp ──────────────────────────────────────────────────────────────────────────────FM/Db2 (DFG2)Alter Table - ADD FOREIGN KEY Constraint Table Identification: Owner . . . . ...