MySQL删除前触发器的正确​​语法是什么？

Question

I'd like to create a before delete trigger that deletes rows from two different tables. But I can't figure out which parameters to use.

I got a house table, and when I delete a row, I'd like to delete every row in my two other tables: user_house and firm_house, which contains same house id as the one triggering the event.

What does FOR EACH ROW mean? And how can I properly set my trigger up?

USE `mydb`;
DELIMITER $$
CREATE TRIGGER `deleteUnions` BEFORE DELETE ON `house` 
FOR EACH ROW
BEGIN
    DELETE FROM user_house WHERE ?? = ??; 
    DELETE FROM firm_house WHERE ?? = ??;
END

Some details about the structure:

• user_house is joined by user_id and house_id ;
• firm_houise is joined by firm_id and house_id .

Answer 1

Refer to the record that gets deleted in the trigger with OLD . Then use the id to delete from the other tables.

DELETE FROM user_house WHERE house_id = OLD.house_id; 
DELETE FROM firm_house WHERE house_id = OLD.house_id;