Question

I have two tables:

Requests – Request_id , Request_Message; // contains Requests

Responses – Response_id , Request_id , Response_Message; // Contains Responses for the request..
Request_id is foreign key for this table

Now while i am running the query delete from requests where Request_id = “REQ001”;.... if there is no corresponding response in responses table then query is working fine, other its giving foreign key constraint error.

I want while i delete any request from requests table all its corresponding responses must delete automatically from response table.. How to achieve this??

Thanks for your time..

Devesh

Answer 1

Using CASCADE in the definition of the FOREIGN KEY constraint is an option. However, I recommend using the multiple-table syntax of the delete statement, e.g.:

DELETE FROM Requests, Responses
USING Requests
LEFT JOIN Responses ON Requests.Request_id=Responses.Request_id
WHERE Requests.Request_id='REQ001';

This is my preferred solution because it makes more explicit what actually happens.