SQL limit SELECT but not JOIN

Question

I\'m implementing pagination on my BD. My problem is when I want limit the SELECT statement but not the JOIN. Example, a product can got many prices:

SELECT * FR         


        

Answer 1

Modify your query to limit the number of product rows before joining it to the price table. This means we want to to join the results of a query to a table, or in other words, we write a query containing a subquery:

SELECT *
FROM (
    SELECT *
    FROM product
    ORDER BY id_product
    LIMIT 3
) p
LEFT JOIN price ON p.id = price.id_product

Hope that helps.

Answer 2

I would write a subquery to get the three first products (or whatever condition you choose) like this:

SELECT id
FROM product
ORDER BY id
LIMIT 3;

Once I have that, I can select everything from the price table as long as the id is in that subquery. You can do this using a join:

SELECT p.*
FROM price p
JOIN(
   SELECT id
   FROM product
   ORDER BY id
   LIMIT 3) tmp ON tmp.id = p.product_id;

Here is an SQL Fiddle example using your sample data, and I also added a row that won't be returned so you can see that it works.