Using same column multiple times in WHERE clause

Question

I have a following table structure.

USERS

PROPERTY_VALUE

PROPERTY_NAME

USER_

Answer 1

If you just want the distinct columns in U, it is:

SELECT DISTINCT u.* 
  FROM Users u INNER JOIN USER_PROPERTY_MAP upm ON u.id = upm.[user_id]
                INNER JOIN PROPERTY_VALUE pv ON upm.property_value_id = pv.id
                INNER JOIN PROPERTY_NAME pn ON pv.property_name_id = pn.id

  WHERE (pn.id = 1 AND pv.[value] = '101')
     OR (pn.id = 2 AND pv.[value] = '102')

Notice I used pv.[value] = instead of the subquery to reacquire id... this is simplification.

Answer 2

If you want just to filter:

SELECT users.*
FROM users
where (
    select count(*)
    from user_property_map
    left join property_value on user_property_map.property_value_id = property_value.id
    left join property_name on property_value.property_name_id = property_name.id
    where user_property_map.user_id = users.id -- join with users table
    and (property_name.name, property_value.value) in (
        values ('property1', '101'), ('property2', '102') -- filter properties by name and value
    )
) = 2 -- number of properties you filter by

Or, if you need users ordered descending by number of matches, you could do:

select * from (
    SELECT users.*, (
        select count(*) as property_matches
        from user_property_map
        left join property_value on user_property_map.property_value_id = property_value.id
        left join property_name on property_value.property_name_id = property_name.id
        where user_property_map.user_id = users.id -- join with users table
        and (property_name.name, property_value.value) in (
            values ('property1', '101'), ('property2', '102') -- filter properties by name and value
        )
    )
    FROM users
) t
order by property_matches desc