如何更改约束

下面是我的约束条件之一

CONSTRAINT ACTIVEPROG_FKEY1 FOREIGN KEY(ActiveProgCode) REFERENCES PROGRAM(ActiveProgCode),

我想加上

ON DELETE CASCADE

对上述约束。

如何修改现有约束 ACTIVEPROG _ FKEY1并添加

ON DELETE CASCADE

约束 ACTIVEPROG _ FKEY1

考虑 ACTIVEPROG _ FKEY1位于表 ACTIVEPROG

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No. We cannot alter the constraint, only thing we can do is drop and recreate it

ALTER TABLE [TABLENAME] DROP CONSTRAINT [CONSTRAINTNAME]

Foreign Key Constraint

Alter Table Table1 Add Constraint [CONSTRAINTNAME] Foreign Key (Column) References Table2 (Column) On Update Cascade On Delete Cascade

Primary Key constraint

Alter Table Table add constraint [Primary Key] Primary key(Column1,Column2,.....)

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最佳答案

You can not alter constraints ever but you can drop them and then recreate.

Have look on this

ALTER TABLE your_table DROP CONSTRAINT ACTIVEPROG_FKEY1;

and then recreate it with ON DELETE CASCADE like this

ALTER TABLE your_table
add CONSTRAINT ACTIVEPROG_FKEY1 FOREIGN KEY(ActiveProgCode) REFERENCES PROGRAM(ActiveProgCode)
ON DELETE CASCADE;

hope this help