Question

I WANT TO DO SOMETHING LIKE THIS:

CREATE TRIGGER addwinner AFTER INSERT ON bids
FOR EACH ROW BEGIN 
IF exists(select * from wins as LT where LT.item_index=NEW.item_index) THEN

SELECT item_index, MIN( bid_amount ) 
FROM update_winnerslist AS a1
WHERE a1.item_index =  NEW.item_index;
UPDATE wins SET email_id=NEW.emai_id, bid_amount=a1.bid_amount where wins.item_index=a1.item_index;

END IF;
END;

Basically what i want is to update a table using another table’s tuple by comparing certain attributes.

Answer 1

As explained in the manual, when defining procedures/triggers/etc. that use ; within their body to separate commands, you need to define an alternate delimiter in order that the CREATE command is interpreted as a single statement.

To UPDATE with the results of the SELECT, like you describe, you can do any of:

1. Save the result of the SELECT in a variable which you then use in the UPDATE:

   DELIMITER ;; -- or anything else you like
   
   CREATE TRIGGER addwinner AFTER INSERT ON bids FOR EACH ROW
     IF EXISTS (SELECT * FROM wins AS LT WHERE LT.item_index=NEW.item_index)
     THEN
       SELECT MIN(bid_amount) INTO @bid_amount
       FROM   update_winnerslist AS a1
       WHERE  a1.item_index = NEW.item_index;
   
       UPDATE wins
       SET    email_id=NEW.emai_id, bid_amount=@bid_amount
       WHERE  wins.item_index=a1.item_index;
     END IF;;  -- whatever command delimiter you chose above goes here
   
   DELIMITER ; -- reset to normal
   

2. Just use a subquery (so long as it doesn’t reference the table you’re updating):

   DELIMITER ;; -- or anything else you like
   
   CREATE TRIGGER addwinner AFTER INSERT ON bids FOR EACH ROW
     IF EXISTS (SELECT * FROM wins AS LT WHERE LT.item_index=NEW.item_index)
     THEN
       UPDATE wins
       SET    wins.email_id=NEW.emai_id, wins.bid_amount=(
         SELECT MIN(bid_amount)
         FROM update_winnerslist AS a1
         WHERE a1.item_index = NEW.item_index
       )
       WHERE  item_index = NEW.item_index
     END IF;;  -- whatever command delimiter you chose above goes here
   
   DELIMITER ; -- reset to normal
   

3. Or just join the tables:

   DELIMITER ;; -- or anything else you like
   
   CREATE TRIGGER addwinner AFTER INSERT ON bids FOR EACH ROW
     IF EXISTS (SELECT * FROM wins AS LT WHERE LT.item_index=NEW.item_index)
     THEN
       UPDATE wins JOIN update_winnerslist AS a1 USING (item_index)
       SET    wins.email_id=NEW.emai_id, wins.bid_amount=MIN(a1.bid_amount);
       WHERE  item_index = NEW.item_index
     END IF;;  -- whatever command delimiter you chose above goes here
   
   DELIMITER ; -- reset to normal