Question

we have a DB which stores users who may have pictures.

I am looking for an elegant way in SQL to get the following results:
Select n users. Of those n users e.g. 60% should have an associated picture and 40% should not have a picture. If there are less than 60% users having a picture the result should be filled up with users wihtout an image.

Is there some elegant way in SQL without firing multiple SELECTs to the DB?

Thank you very much.

Answer 1

Ugly code:

SELECT TOP @n * FROM
(


      //-- We start selecting users who have a picture (ordered by HasPicture)
      //-- If there is no more users with a picture, this query will fill the 
      //-- remaining rows with users without a picture
      SELECT TOP 60 PERCENT * FROM tbUser
      ORDER BY HasPicture DESC

      UNION

      //-- This is to make sure that we select at least 40% users without a picture
      //-- AT LEAST because in the first query it is possible that users without a 
      //-- picture have been selected
      SELECT TOP 40 PERCENT * FROM tblUser
      WHERE HasPicture = 0

      //-- We need to avoid duplicates because in the first select query we haven't 
      //-- specified HasPicture = 1 (and we didn't want to).
      AND UserID not IN
      (
        SELECT TOP 60 PERCENT UserID FROM tbUser
        ORDER BY HavePicture DESC
      )
 )