Deleting hierarchical data in SQL table

Question

I have a table with hierarchical data.
A column \"ParentId\" that holds the Id (\"ID\" - key column) of it\'s parent.

When deleting a row, I want to delete all c

Answer 1

Add a foreign key constraint. The following example works for MySQL (syntax reference):

ALTER TABLE yourTable
ADD CONSTRAINT makeUpAConstraintName
FOREIGN KEY (ParentID) REFERENCES yourTable (ID)
ON DELETE CASCADE;

This will operate on the database level, the dbms will ensure that once a row is deleted, all referencing rows will be deleted, too.