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No Need for trigger Re: oracle trigger question

No Need for trigger Re: oracle trigger question# Database - 数据库

B*n2001-01-15 08:01

1 楼

In this case, you dont even need a trigger. It is
automatically
handled by database referential constraints. Basically you
need
to specify the DELETE CASCADE constraint when creating table
A
that has a forien key referencing table B.
here is an example:
suppose you have the table B which has deptno as a primary
key:
SQL> select * from B;
DEPTNO DNAME LOC

h*r2001-01-15 08:01

2 楼

Thanks a lot,
my worry is if I do:
SQL>delete B;
Will it also remove the related items in the table A
automatically? That means we will not delete records
from table B one by one, but delete all at the same
time, will the referential work?

【在 B*****n 的大作中提到】

: In this case, you dont even need a trigger. It is
: automatically
: handled by database referential constraints. Basically you
: need
: to specify the DELETE CASCADE constraint when creating table
: A
: that has a forien key referencing table B.
: here is an example:
: suppose you have the table B which has deptno as a primary
: key:

B*n2001-01-15 08:01

3 楼

at least in Oracle, you will not be able to drop table B if
there are still rows in A that have foreign keys referencing
B. you will get an error if you try to drop B.

【在 h****r 的大作中提到】

: Thanks a lot,
: my worry is if I do:
: SQL>delete B;
: Will it also remove the related items in the table A
: automatically? That means we will not delete records
: from table B one by one, but delete all at the same
: time, will the referential work?