从表中删除SQL中的行

Question

Sorry for the title but I didn't know how to name it..

I'm using C# and have a WinForms application I have 2 tables, each of them have a primary key, those 2 tables are strangers. It means that I have a third table that connects between them. the third table have as columns : table's A primary key and table's B primary key.

I just want to know that if I'm deleting one row from the third table, is the related data from table A and B will be also deleted?

Answer 1

If you created a foreign key constraint with the ON DELETE CASCADE option, then yes, it will delete the related rows in other tables.

If you created a foreign key constraint WITHOUT the ON DELETE CASCADE option, then the DBMS will prevent you from deleting the original row at all.

If you did not create a foreign key constraint then only the original row will be deleted.

See this SO answer for example usage of the cascading delete option.

Answer 2

No, it doesn't your third table is just associate table which stores references of table A and B.

But it will have different functionality other way, if a record is deleted in table A and it has any references in associate table C. Depending upon your cascade options, record in table C will also be deleted. If there are no cascade options mentioned, it gives exception.

Answer 3

Sql Server wouldn't let you delete the row from 3rd table because of a Foreign Key constraint. You'd have to delete the values referencing the 3rd table from table A and B first and then delete from your 3rd table.

Answer 4

否，因为第三个表是表a和表b的关联表，如果删除在第三个表上，则不会删除表a和表b中的记录。