SQLServer FOREIGN KEY ON DELETE CASCADE 限制条件 在需要实现级联删除的情况下,使用 FOREIGN KEY的ON DELETE CASCADE选项非常方便,但在同一张表中,如果有两个外键引用外表数据,那么最多只能将一个外键设为 ON DELETE CASCADE,其他的引用约束需要使用触发器实现级联删除。 1--建立单词表2IF
CONSTRAINT`s_id`FOREIGN KEY (`student_id`) REFERENCES`student`(`id`) ) 3 更改事件触发限制为 CASCADE #删除旧的外键 ALTERTABLEstudent_scoreDROPFOREIGNKEY s_id; #添加新的外键,修改事件触发限制为 CASCADE ALTERTABLEstudent_score ADDCONSTRAINTs_idFOREIGNKEY (student_id)REFERENCESstudent (id) ONDELETEC...
After drop a table,create one new table with foreign key with on delete cascde option CREATE TABLE STUDENT_ADDRESS(ADDRESS VARCHAR2(10),S_ID NUMBER,CONSTRAINT SS_ADD_FKFOREIGN KEY (S_ID) REFERENCES STUDENT(S_ID) ON DELETE CASCADE); INSERT INTO STUDENT_ADDRESS VALUES('JMD',1);INSERT INTO...
select * from information_schema.KEY_COLUMN_USAGE;
aler table 表名称 [constraint 外键名称] add foreign key(外键字段) references 主表名称(主键字段); 1. 修改外键 & 删除外键 外键不可以修改:只能先删除再追加 删除外键语法 alter table 表名称 drop foreign key 外键名称; -- 一张表中可以有多个外键,每个外键名称不能相同 ...
primary key clustered(id asc) with(ignore_dup_key=off) on [primary], --主键索引声明 constraint 外键名 foreign key(列名) references 主表名(列名) on update cascade--是否级联操作 on delete cascade )on [primary] --字段注释声明 exec sys.sp_addextendedproperty @name=N'MS_Description', @value=...
ondeletecascade); 此时再去修改: 得到结果: 此时再去删除: 得到结果: 多对多的关系: 两张表记录之间是一个双向的多对一关系,称之为多对多关系。 如何实现? 建立第三张表,该表中有一个字段foreign key左表的id,还有一个字段是foreign key右表的id ...
alter table 数据库名.[dbo].表名 with check add constraint 约束名 foreign key(列名) references 数据库名.[dbo].表名(列名) on delete cascade on update cascade; go 示例: if exists(select * from sysobjects where name='t1_t2') alter table [testss].[dbo].[test1] drop constraint t1_t2; ...
ADD CONSTRAINT [FK_OrderDetail_Order] FOREIGN KEY([OrderID]) REFERENCES [dbo].[Order] ([OrderID]) ON DELETE CASCADE GO — data load DECLARE @val BIGINT DECLARE @val2 BIGINT SELECT @val=1 WHILE @val < 100000 BEGIN INSERT INTO dbo.[Order] VALUES(@val,’TEST’ + CAST(@val AS VARCH...
The syntax for creating a foreign key with cascade delete in an ALTER TABLE statement in Oracle/PLSQL is: ALTER TABLE table_name ADD CONSTRAINT constraint_name FOREIGN KEY (column1, column2, ... column_n) REFERENCES parent_table (column1, column2, ... column_n) ON DELETE CASCADE; Examp...