如何改变约束
本文介绍了如何改变约束的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
SQL 如何改变约束
以下是我的约束条件之一
Below is 1 of my constraint
CONSTRAINT ACTIVEPROG_FKEY1 FOREIGN KEY(ActiveProgCode) REFERENCES PROGRAM(ActiveProgCode),
我想加入
ON DELETE CASCADE
到上面的约束.
如何更改现有约束 ACTIVEPROG_FKEY1 并添加
How do i alter that existing constraint ACTIVEPROG_FKEY1 and add
ON DELETE CASCADE
约束ACTIVEPROG_FKEY1
to constraint ACTIVEPROG_FKEY1
考虑 ACTIVEPROG_FKEY1 在表 ACTIVEPROG
Consider ACTIVEPROG_FKEY1 is at Table ACTIVEPROG
推荐答案
你永远不能改变约束，但你可以删除它们然后重新创建.
You can not alter constraints ever but you can drop them and then recreate.
看看这个
ALTER TABLE your_table DROP CONSTRAINT ACTIVEPROG_FKEY1;
然后像这样用ON DELETE CASCADE重新创建它
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;
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