Table1
val(int)
---
1
3
5
9
Table2
val(int)
---
4
9
14
17
we want to return
val val
--- ---
1 4
3 9
5 14
9 17
And we want to achieve this WITHOUT the use of cursors (obviously!).
If we could assign a row number to each table then we can join on the row number, row1 = row1, row2=row2, etc... now SQL 2005 gives us a couple of ways of doing this using either the RANK() function or the ROW_NUMBER() function.
if object_id('tempdb..#t1') is not null drop table #t1
if object_id('tempdb..#t2') is not null drop table #t2
create table #t1 (val int)
create table #t2 (val int)
insert into #t1 values (1)
insert into #t1 values (3)
insert into #t1 values (5)
insert into #t1 values (9)
insert into #t2 values (4)
insert into #t2 values (9)
insert into #t2 values (14)
insert into #t2 values (17)
using RANK()
select t3a.val, t3b.val
from
(select val, rank() over (order by val) as seq from #t1) t3a
join
(select val, rank() over (order by val) as seq from #t2) t3b
on t3a.seq=t3b.seq
or using ROW_NUMBER()
select t3a.val, t3b.val
from
(select val, row_number() over (order by val) as seq from #t1) t3a
join
(select val, row_number() over (order by val) as seq from #t2) t3b
on t3a.seq=t3b.seq
But in SQL2000 these functions do not exist. An elegant way to achieve this is to join the table to itself and determine the 'rank' by counting the number of elements that are less than or equal to the current i.e.
select t11.val, count(*) as seq
from #t1 t11, #t1 t12 where t11.val>=t12.val group by t11.val
returns
val seq
--- ---
1 1
3 2
5 3
9 4
hence we can use this as the ranking function
select t3a.val, t3b.val
from
(select t11.val, count(*) as seq
from #t1 t11, #t1 t12 where t11.val>=t12.val group by t11.val) t3a
join
(select t21.val, count(*) as seq
from #t2 t21, #t2 t22 where t21.val>=t22.val group by t21.val) t3b
on t3a.seq=t3b.seq
[Credit goes to Richard Dean for the original idea]
