On 4/11/07,
Raymond O'Donnell <
rod@iol.ie> wrote:
Hi all,
This is probably a very simple one, but I just can't see the answer and
it's driving me nuts. I have a table holding details of academic terms,
and I need an SQL query such that for any given term I want to find the
next term by starting date (or just NULL if there isn't one).
Here's the table -
CREATE TABLE terms
(
term_id serial NOT NULL,
term_name character varying(40) NOT NULL,
term_starts date NOT NULL,
term_ends date NOT NULL,
.....
)
- so, supposing I have the following data -
term_id | term_name | term_starts | ...
---------+-------------+-------------+--
1 | Spring 2007 | 2007-01-10 | ...
2 | Autumn 2007 | 2007-09-01 | ...
6 | Spring 2008 | 2008-01-06 | ...
- then for term '1' I'd like to return '2', for term '2' I'd like to
return '6', and so on.
The closest I've got is getting ALL terms that start after a given one,
but I run into trouble after that....any help will be appreciated!
Thanks in advance,
Ray.
---------------------------------------------------------------
Raymond O'Donnell, Director of Music, Galway Cathedral, Ireland
rod@iol.ie
---------------------------------------------------------------
SELECT main.term_name,
main.term_starts mts,
next.term_name,
next.term_starts nts
FROM terms main
LEFT JOIN terms NEXT
ON main.term_starts < NEXT.term_starts
WHERE NOT EXISTS
(SELECT 1
FROM terms t
WHERE t.term_starts > main.term_starts
AND t.term_starts < NEXT.term_starts)
It's kind of a sneak attack way of getting at the min(term_starts) without using an aggregate.
Jeff
