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.

Answer 2

SELECT  MIN(id), name, parent_id, school_id
  FROM  Table
WHERE   name <> 'unknown'
GROUP BY name, parent_id, school_id
UNION ALL
SELECT  id, name, parent_id, school_id
  FROM  Table
 WHERE  name = 'unknown'

Answer 3

SELECT 
  MIN(id) AS id,
  IF(tmpname=id,"unknown",tmpname) AS name,
  parent_id,
  school_id
FROM (
  SELECT 
    id,parent_id,school_id
    IF(name="unknown",id,name) AS tmpname
  FROM <tablename>
) AS baseview
GROUP BY tmpname

Answer 4

You can't easily do this with one statement but you can UNION the results of two statements

• GROUP the list of all but unknown
• Add (UNION) the list of all unknown

SQL Statement

SELECT MIN(id), name, parent_id, school_id
FROM   YourTable
WHERE  name <> 'unknown'
GROUP BY
       name, parent_id, school_id
UNION ALL
SELECT id, name, parent_id, school_id
FROM   YourTable
WHERE  name = 'unknown'

Note that I assume you have posted wrong unknown id's in your result