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,...
如果在 FOREIGN KEY 约束的 ON UPDATE 和/或 ON DELETE 子句中指定 CASCADE 选项,SQL Server 将为 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,SQL Server 则为 UPDATE_RULE 和/或 DELETE_RULE 列返回 SQL_N...
KEY_SEQ (ODBC 1.0)9Smallint(非 NULL)键 (中的列序列号从 1) 开始。 UPDATE_RULE (ODBC 1.0)10Smallint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。
DELETE_RULE (ODBC 1.0)11Smallint當 SQL 作業為DELETE時,要套用至外鍵的動作。 可以有下列其中一個值。 (參考資料表是具有主鍵的資料表;參考資料表是具有外鍵的資料表。 SQL_CASCADE:刪除參考資料表中的資料列時,也會刪除參考資料表中的所有相符資料列。
KEY_SEQ (ODBC 1.0)9Smallint(非 NULL)键 (中的列序列号从 1) 开始。 UPDATE_RULE (ODBC 1.0)10Smallint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。
This stands when setting Delete Rule is set to “No Action” (this should be how you set your foreign key in most cases). “Cascade” would also delete rows from the child table, while “Set NULL” and “Set Default” wouldn’t delete entire rows from the child table, but just set ...
Foreign_Key_Cascade 算子是执行 DML 语句时,执行外键引用行为的算子。 mysql> explain analyze delete from parent where id = 1; +---+---+---+---+---+---
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 ...
The following example uses a single-column foreign key to associate the parent table and the child table: CREATE TABLE parent ( id INT KEY ); CREATE TABLE child ( id INT, pid INT, INDEX idx_pid (pid), FOREIGN KEY (pid) REFERENCES parent(id) ON DELETE CASCADE ); The following is a...
Providers should return NULL only if they cannot determine the DELETE_RULE. In most cases, this implies a default ofNO ACTION. PK_NAME DBTYPE_WSTR Primary key name. NULL if the provider does not support named primary key constraints. This column is not returned by 1.xproviders. ...