MySQL trigger: Compare value in another table
Question
I have the following trigger (generated using PHP via mysqli)...
DROP TRIGGER IF EXISTS post_queue_insert;
CREATE TRIGGER post_queue_insert AFTER INSERT ON posts
FOR EACH ROW BEGIN
IF (NEW.post_type != 'revision' AND NEW.post_status != 'auto-draft') THEN
INSERT INTO event_queue (action_id, action_do, action_key, action_value, action_event, action_timestamp, sync_complete, SITE_ID) VALUES (NEW.ID, 'post', NEW.post_type, NEW.post_status, 'insert', UNIX_TIMESTAMP(now()), 0, 1);
END IF;
END;
What I can't figure out is how to check if the 'post_type' value exists in another table and if it doesn't then insert it.
?
Solution
DROP TRIGGER IF EXISTS post_queue_insert;
CREATE TRIGGER post_queue_insert AFTER INSERT ON posts
FOR EACH ROW BEGIN
DECLARE found_it INT;
IF (NEW.post_type != 'revision' AND NEW.post_status != 'auto-draft') THEN
SELECT COUNT(1) INTO found_it FROM some_other_table
WHERE post_type = NEW.post_type;
IF found_it = 0 THEN
INSERT INTO event_queue (action_id, action_do, action_key, action_value, action_event, action_timestamp, sync_complete, SITE_ID) VALUES (NEW.ID, 'post', NEW.post_type, NEW.post_status, 'insert', UNIX_TIMESTAMP(now()), 0, 1);
END IF;
END IF;
END;
If found_it = 0, then the row does not contain a value matching NEW.post_type.
Give it a Try !!!
OTHER TIPS
DROP TRIGGER IF EXISTS post_queue_insert;
CREATE TRIGGER post_queue_insert AFTER INSERT ON posts
FOR EACH ROW BEGIN
IF ( NEW.post_type != 'revision'
AND NEW.post_status != 'auto-draft'
AND NOT EXISTS
( SELECT *
FROM other_table
WHERE post_type = NEW.post_type
)
)
THEN
INSERT INTO event_queue (action_id, action_do, action_key, action_value, action_event, action_timestamp, sync_complete, SITE_ID)
VALUES (NEW.ID, 'post', NEW.post_type, NEW.post_status, 'insert', UNIX_TIMESTAMP(now()), 0, 1);
END IF;
END;
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