On the other hand, if it chooses t1 -- t3, it fails with "child record found". Now my question is what strategy oracle uses to choose the delete path. It would appear we cascade the delete and then check: CREATE TABLE t1 (x INT PRIMARY KEY); CREATE TABLE t2 (y INT PRIMARY KEY,...
SQLForeignKeys SQL Server 通过外键约束机制支持级联更新和删除操作。如果在 FOREIGN KEY 约束的 ON UPDATE 和/或 ON DELETE 子句中指定 CASCADE 选项,SQL Server 将针对 UPDATE_RULE 和/或 DELETE_RULE 列返回 SQL_CASCADE。如果未在 FOREIGN KEY 约束的 ON UPDATE 和/或 ON DELETE 子句中指定 NO ACTION 选项...
如果对 FOREIGN KEY 约束的 ON UPDATE 和/或 ON DELETE 子句指定 CASCADE 选项,则 SQL Server 将返回UPDATE_RULE和/或DELETE_RULE列的SQL_CASCADE。 如果在 FOREIGN KEY 约束的 ON UPDATE 和/或 ON DELETE 子句上指定 NO ACTION 选项,则 SQL Server 将返回UPDATE_RULE和/或DELETE_RULE列的SQL_NO_ACTION。
KEY_SEQ (ODBC 1.0) 9 Smallint(非 NULL) 键(中的列序列号从 1) 开始。 UPDATE_RULE (ODBC 1.0) 10 Smallint 当SQL 操作为 UPDATE 时要应用于外键的操作。 可以具有以下值之一。 (引用的表是具有主键的表;引用表是具有外键的表) SQL_CASCADE:更新引用表的主键时,引用表的外键也会更新。 SQL_NO_ACT...
if (delete_rule == SQL_NO_ACTION) { printf("NO ACTION "); /* non-IBM only */ } else { printf("SET NULL "); } } } printf("\n"); if (pkey_name.ind > 0 ) { printf(" Primary Key Name: %s\n", pkey_name.s);
After this, right-click on the Primary key icon. Now, the following options will appear. Set Delete Rule This is one of the main key items that we have to discuss in detail. There are 4 delete rules: No Action Cascade Set Null Set Default Rule 1 - No Action This is the default ...
CASCADE(跟随外键改动) SET NULL(设空值) SET DEFAULT(设默认值) NO ACTION(无动作,默认的) 搞个例子,简单演示一下使用,做dage和xiaodi两个表,大哥表是主键,小弟表是外键: 建表: 11CREATETABLE`dage` (22`id`int(11)NOTNULLauto_increment,33`name`varchar(32)default'',44PRIMARYKEY(`id`)55) ENGINE=...
For the DELETE rule we are using CASCADE For the UPDATE rule we are using CASCADE That's all there is to it. Create Foreign Key Using SSMS GUI To create a Foreign Key using the SSMS GUI, using Object Explorer select the referencing table dbo.Product, go to Keys, right click on Keys ...
Delete rule The delete rule of a referential constraint is specified when the referential constraint is defined. The choices are NO ACTION, RESTRICT, CASCADE, or SET NULL. SET NULL can be specified only if some column of the foreign key allows null values. ...
ON DELETE CASCADE GO Now on the Cities table, create a foreign key without a DELETE CASCADE rule. 1 2 3 ALTER TABLE [dbo].[Cities] WITH CHECK ADD CONSTRAINT [FK_Cities_States] FOREIGN KEY([StateID]) REFERENCES [dbo].[States] ([StateID]) GO If we try to delete a record with ...