Group By Except For Certain Value

Question

I\'m trying to create a (sqlite) query that will perform a GROUP BY but will not group anything with the value \'unknown\'. For example, I have the table:

i         


        

Answer 1

As a single query...

SELECT
  MIN(id)            AS id,
  name,
  parent_id,
  school_id
FROM
  yourTable
GROUP BY
  CASE WHEN name = 'unknown' THEN id ELSE 0 END,
  name,
  parent_id,
  school_id

Or possibly...

GROUP BY
  CASE WHEN name <> 'unknown' THEN name ELSE CAST(id AS VARCHAR(???)) END,
  parent_id,
  school_id

-- Where VARCHAR(???) is the data type of the `name` field.
-- Also assumes no value in `name` is the same as an id for an 'unknown' field

Both avoid UNION and the overhead of parsing the table twice, replacing it with a slightly increased complexity GROUP BY.