Question

Can I do this to update a row? This is the first time I am using a LEFT JOIN with an UPDATE.

UPDATE comments AS r

LEFT JOIN items AS i 
        ON i.items_id = r.item_id
LEFT JOIN master_cat AS c
        ON c.cat_id = i.items_id  
SET r.good = r.good + 1 
WHERE i.item = '{$item}' AND c.category = '{$cat}' AND r.review = '{$review}';

It doesn’t throw an error, but it says 0 rows affected even though I have confirmed my variables are ok with right data. (Even if I hard code the data).

Edit: I have tried inner join as well, and does not work either.

Edit 2: This is actually what I am trying to do, I have these two queires and they work fine. I am trying to simplify code to one. Can this be done:

     // This query returns rate_id which I use as "$review_id" in the second query.

     $query = "
     SELECT r.rate_id
     FROM comments as r
     LEFT JOIN items AS i 
         ON i.items_id = r.item_id
     LEFT JOIN master_cat AS c
         ON c.cat_id = i.cat_id
     WHERE r.review = '{$review}' 
        AND i.item = '{$item}' 
        AND c.category = '{$cat}';"; 

    $query = "
    UPDATE comments 
    SET good = good + 1 
    WHERE rate_id = '{$review_id}';";

Answer 1

Your problem is that in the UPDATE statement you have a mismatching join (cat_id with items_id):

LEFT JOIN master_cat AS c
        ON c.cat_id = i.items_id  

while in the SELECT (that is working), you have the join correctly:

LEFT JOIN master_cat AS c
        ON c.cat_id = i.cat_id