具有外键约束的SQL删除查询

Question

I know that this question belongs to the very early stages of the database theory, but I have not encountered such a problem since several months. If someone has a database with some tables associated together as "chain" with foreign keys and they want to delete a record from a table which has some "dependent" tables, what obstacles arise? In particular, in a database with tables: Person, Profile, Preference, Filter exist the associations as Person.id is foreign key in Profile and Profile.id is foreign key in Preference and Filter.id is foreign key in Preference , so as that all the associations enter code here are OneToMany . Is it possible to delete a Person with a simple query:

Delete from Person p where p.id= 34;

If no, how should look like the query in order to perform the delete successfully? If the database in the application is managed by hibernate, what constraints ( annotations ) should I apply to the associated fields of each entity, so as to be able with the above simple query to perform the delete?

Answer 1

FOR SQL VERSION

Look at the Screenshot. you can use the Insert Update Specificaiton Rules. as it has Delete and Update Rules. you can set either of these values.

Foreign key constraints may be created by referencing a primary or unique key. Foreign key constraints ensure the relational integrity of data in associated tables. A foreign key value may be NULL and indicates a particular record has no parent record. But if a value exists, then it is bound to have an associated value in a parent table. When applying update or delete operations on parent tables there may be different requirements about the effect on associated values in child tables. There are four available options in SQL Server 2005 and 2008 as follows:

No Action
Cascade
SET NULL
SET Default

Use this article for Refrence.

http://www.mssqltips.com/sqlservertip/2365/sql-server-foreign-key-update-and-delete-rules/

ORACLE VERSION

you can use one of below.

alter table sample1 add foreign key (col1) references sample (col2) on delete no action;

alter table sample1 add foreign key (col1) references sample (col2) on delete restrict;

alter table sample1 add foreign key (col1) references sample (col2) on delete cascade;

for refrance.

http://docs.oracle.com/cd/B19306_01/server.102/b14200/clauses002.htm

Answer 2

answer is no if there is foreign key constraint then you have to delete leaf node table data first

that is first delete from Preference table

then from Profile and Filter Table

then delete record from Person table

This is the generic concept that you apply anywhere