ORDER BY the IN value list

Question

I have a simple SQL query in PostgreSQL 8.3 that grabs a bunch of comments. I provide a sorted list of values to the IN construct in the WHERE clause:

SELECT * FROM comments WHERE (comments.id IN (1,3,2,4));

This returns comments in an arbitrary order which in my happens to be ids like 1,2,3,4.

I want the resulting rows sorted like the list in the IN construct: (1,3,2,4).

How to achieve that?

Answer 1

It'll be quite easy to do with VALUES (), () which is introduced in PostgreSQL 8.2.

Use the below query:

select c.*

from comments c

join (

  values

    (1,1),

    (3,2),

    (2,3),

    (4,4)

) as x (id, ordering) on c.id = x.id

order by x.ordering