Re: ORDER BY using specifc values

Ian McWilton <ian@blazingcactus.com> writes:
> I need to return the results of a SELECT ordered by a 
> column but in a way that is neither ascending or 
> descending. 

> The ORDER BY column can have one of five values and I 
> want to specify which values are returned in the list 
> in which order.

> An example table below shows the data in the DB:

> INDEX | VALUE
> 1, A
> 2, B
> 3, B
> 4, C
> 5, B

> ...and what I want is for my queries result to be 
> ordered by VALUE with C put first in the list, then A, 
> then B.

> Having investigated it appears that ORDER BY does not 
> seem to be any help as it restricts the ordering to ASC 
> or DESC.

Make a function f(x) that converts the stored values into a suitable
ordering, say C -> 1, A -> 2, B -> 3.  Then doORDER BY f(column)

If you have no more-elegant ideas at hand, f() could be defined
using a CASE expression.  In fact you could just write the CASE
expression right in ORDER BY, but if you need the same ordering
in many different queries then defining a function is probably
the way to go.
        regards, tom lane