Question

I’m having a problem with fetching some data.
The tables I have (for testing purposes):

Products:

product_id      | product_name
-----------------------------
1               | product 1
2               | product 2
3               | product 3

Attributes:

product_id      | attribute_id      | attribute_value
-------------------------------------------------------
1               | 1                 | lorem
1               | 2                 | ipsum
2               | 1                 | lorem
2               | 2                 | doler
3               | 1                 | sit
3               | 2                 | ipsum

I want to find the products that have lorem stored in attribute_id 1 AND ipsum stored in attribute_id 2.

If I use this query,

SELECT
   attributes.attribute_id,
   attributes.attribute_value,
   products.product_id
FROM
   products
   Inner Join attributes ON products.product_id = attributes.product_id
WHERE
   (attributes.attribute_id = 1 AND attributes.attribute_value = 'lorem')
OR
   (attributes.attribute_id = 2 AND attributes.attribute_value = 'ipsum')

I get:

attribute_id         | attribute_value     | product_id
----------------------------------------------------------
1                    | lorem               | 1
2                    | ipsum               | 1
1                    | lorem               | 2
2                    | lorem               | 3

But I really want to get this result:

attribute_id_1 | attribute_id_2 | attribute_value_1 | attribute_value_2 | product_id
----------------------------------------------------------
1              | 2              | lorem             | ipsum             | 1

Or just product_id 1 as a result.

I can get it working with the next query, but in production (with a lot of data and a few more joins) this is WAY to slow.

SELECT
   products.product_id
FROM
   products
   Inner Join attributes ON products.product_id = attributes.product_id
WHERE
   attributes.attribute_value = 'ipsum'
AND
   products.product_id IN (
      SELECT
         products.product_id
      FROM
         products
         Inner Join attributes ON products.product_id = attributes.product_id
      WHERE
         attributes.attribute_value =  'lorem'
)

I hope you understand what I’m trying to do.

Can someone please help me?
Thanks!

Answer 1

Could you take the first (broken) query, group by product_id and then add a HAVING COUNT(*) = 2 clause?