A quick SQL poll

25th February, 2011

Tweet

Today's writing is really short and is a poll. So please use the comment feature to answer it. Let consider the tables below for a relational schema about people owning pictures (I suppose that a BLOB column could hold the picture, but this is not important here):

Now, consider the following SQL query that returns the whole people info as well as the number of pictures each of them has in the database:

SELECT id, 
       email,
       name,
       (SELECT count(*) 
          FROM pictures
          WHERE pictures.owner = people.id) as nb_picts
  FROM people

Here is the poll. How do you feel?

1. Exactly what you'd have written
2. You prefer to use a GROUP BY
3. It's probably correct, but you're not sure
4. You would never write such a query, it's certainly inefficient
5. The query is incorrect, not allowed in SQL
6. Other (please explain)

Post your response as a 1-6 number using the comment feature below (there is no particular trap).

Thanks!