Is there a way to split the results of a select query into two equal halfs?

Question

I need a solution for a select query in Sql Server 2005.

I\'d like to have a query returning two ResultSets each of which holding exactly half of all records matchin

Answer 1

SQL Server 2005 and similar:

select *, ntile(2) over(order by theid) as tile_nr from thetable

ntile(n) allocates the output into n segments, each of the same size (give or take rounding when the number of rows isn't divisible by n). So this produces the output:

1 | value1 | 1
2 | value2 | 1
3 | value3 | 1
4 | value4 | 2
5 | value5 | 2

If you just want the top or bottom half, you need to put this into a subquery, e.g.:

select theid, thevalue from (
  select theid, thevalue, ntile(2) over(order by theid) as tile_nr from thetable
) x
where x.tile_nr = 1

will return the top half, and similarly use x.tile_nr = 2 for the bottom half