SQL Selecting “Window” Around Particular Row

Question

It\'s quite possible a question like this has been asked before, but I can\'t think of the terms to search for.

I\'m working on a photo gallery application, and want

Answer 1

If you are using SQL Server, you can use the row_number() function to give you the row order index and do something like this:

declare @selected_photo integer;
set @selected_photo = 5;

declare @buffer_size integer;
set @buffer_size = 2;

select
   ph.rownum,
   ph.id
from
   (select row_number() over (order by Id) as rownum, * from Photos) as ph
where
   ph.rownum between case
                         when @selected_photo - @buffer_size < 1 then 1
                         else @selected_photo - @buffer_size
                      end
                      and @selected_photo + @buffer_size

Edit: Here is an article on simulating the row_number() function in MySQL, combining that with this might get you what you need - I'd try it but don't have a MySQL db handy to play with at work. :-)

http://www.xaprb.com/blog/2006/12/02/how-to-number-rows-in-mysql/