Question

I’m trying to get multiple attributes (e.g bedrooms, bathrooms, etc) from a few tables yes I can only seem to get one attribute with my current query. What am I missing?

What I am ultimately trying to find is property_id’s with 2 bathrooms and 2 bedrooms. In this case, my desired results are property id’s 1 and 4.

Here’s my example on sqlfiddle

Example tables:

property
--------
id 
1
2
3
4

attribute
---------
id name
1  bedrooms
2  bathrooms

attribute_value
---------------------
id attribute_id value
1  1            1
2  1            2
3  1            3
4  2            1
5  2            2
6  2            3

property_attributes
------------------------------
property_id attribute_value_id
1           2
1           5
2           2
2           4
3           1
3           4
4           2
4           5 

This query can produce the results I want if I only want to see a query based on single attribute:

SELECT p.property_id
FROM property p
INNER JOIN property_attribute pa ON p.property_id = pa.property_id
INNER JOIN property_area pc ON p.property_id = pc.property_id
WHERE pa.attribute_value_id
IN (
SELECT av.attribute_value_id
FROM attribute_value av
INNER JOIN attribute a ON av.attribute_id = a.attribute_id
WHERE a.name like 'bedrooms' AND av.value like '2')

But what must I do to get results with more attributes (e.g. WHERE a.name like ‘bathrooms’ AND av.value like ‘2’)? If I add another subquery in the main where clause, it doesn’t return any results.

/// EDIT ///

here is the solution that worked for me if anyone else winds up in such a situation:

SELECT p.property_id
FROM property p
INNER JOIN property_attribute pa ON p.property_id = pa.property_id
INNER JOIN property_attribute pa2 ON p.property_id = pa2.property_id
INNER JOIN property_attribute pa3 ON p.property_id = pa3.property_id
WHERE pa.attribute_value_id = 2 
AND pa2.attribute_value_id = 5
AND pa3.attribute_value_id = 7

This makes usage of a self-join.

Answer 1

You have an awful lot of indirection in your schema. Is there any particular point why you need the property_attribute table? Do you expect a single attribute value to be shared by many properties?

In any case, here is the query for you. Very much in the spirit of the two possible duplicates I mentioned above.

SELECT property.property_id,
       bedrooms.value AS bedrooms,
       bathrooms.value AS bathrooms
FROM property,
     attribute AS bedrooms_attr,
     attribute_value AS bedrooms,
     property_attribute AS bedrooms_prop,
     attribute AS bathrooms_attr,
     attribute_value AS bathrooms,
     property_attribute AS bathrooms_prop
WHERE bedrooms_attr.name = 'bedrooms'
  AND bedrooms.attribute_id = bedrooms_attr.attribute_id
  AND bedrooms.attribute_value_id = bedrooms_prop.attribute_value_id
  AND bedrooms_prop.property_id = property.property_id
  AND bedrooms.value = 2
  AND bathrooms_attr.name = 'bathrooms'
  AND bathrooms.attribute_id = bathrooms_attr.attribute_id
  AND bathrooms.attribute_value_id = bathrooms_prop.attribute_value_id
  AND bathrooms_prop.property_id = property.property_id
  AND bathrooms.value = 2

Thanks for providing a fiddle with data to play with.