Question

I have the following query, which gives me the provider for a given title:

SELECT DISTINCT(provider) FROM 
    (SELECT title, provider FROM financials_raw 
        UNION 
        SELECT title, provider from sales_raw
    ) combined 
        WHERE title = 'Home'

However, this will return NULL provider results as well, how would I exclude all null results?

Answer 1

Further to my comment above, the following query will accomplish the same but be more efficient (as undesirable records are not first being joined in the UNION operation before subsequently being filtered from the materialised table):

  SELECT provider FROM financials_raw WHERE title = 'Home' AND provider IS NOT NULL
UNION
  SELECT provider FROM      sales_raw WHERE title = 'Home' AND provider IS NOT NULL

Note that UNION (without the ALL qualification) implies DISTINCT.