How do i ensure no duplicates with this query

I have this query

SELECT 
    (SELECT keyword FROM url_aliAS WHERE query = CONCAT("category_id" , '=', p2c.category_id)) AS something,
    p.product_id, p.model FROM product AS p 
    JOIN product_to_category p2c ON (p.product_id = p2c.product_id)  
        WHERE p.product_id NOT IN (280, 129, 131)

and the rows being returned have duplicate product_id. For example:-

som开发者_如何转开发ething       product_id  model
NULL            20         18924
barcode_labels  20         18924
NULL            21         18926
barcode_labels  21         18926
NULL            22         30332
barcode_labels  22         30332

I tried DISTINCT on the product_id and I also tried in the WHERE clause "and something is not null" and both failed. Is there a solution to this?

You might want something like this (I also refactored the code a bit). However, if you have more than just barcode_labels as a keyword, you'll still get an additional entry for each other combination.

select
    u.keyword as something,
    product_id,
    p.model
from
    product p
    join product_to_category p2c using (product_id)
    join url_alias u on (u.query = concat("category_id=", p2c.category_id))
where
    u.keyword is not null
    and p.product_id not in (280, 129, 131)

Another way would be to play around with the group by clause to get what you want. Try something like this:

select
    max(u.keyword) as something,
    product_id,
    p.model
from
    product p
    join product_to_category p2c using (product_id)
    join url_alias u on (u.query = concat("category_id=", p2c.category_id))
where
    u.keyword is not null
    and p.product_id not in (280, 129, 131)
group by
    product_id,
    p.model

You can group the records:

SELECT 
(SELECT keyword FROM url_aliAS WHERE query = CONCAT("category_id" , '=', p2c.category_id)) AS something,
p.product_id, p.model FROM product AS p 
JOIN product_to_category p2c ON (p.product_id = p2c.product_id)  
    WHERE p.product_id NOT IN (280, 129, 131)
GROUP BY p.product_id

but you don't have alot of control over which information is displayed after the grouping. In your case, in the something column, should it show NULL or barcode_labels?