Question

Initially, I have two variables x (group variable) and y, now I’d like to create a third variable z which within each group of x starts from 1 and increase by 1 whenever y changes. Please see the following example. Could someone help how I can realize it in sql server 2008?

Thanks a lot!

x: a a a a a a a a b b b b b b b b
y: 0 0 0 1 0 0 2 3 0 1 0 0 2 3 0 0

Finally, I’d like to create z like this:

x: a a a a a a a a b b b b b b b b
y: 0 0 0 1 0 0 2 3 0 1 0 0 2 3 0 0
z: 1 1 1 2 3 3 4 5 1 2 3 3 4 5 6 6

Answer 1

Here is the simple solution:

  declare @temp table ([row] int identity,[x] char,[y] int)
insert into @temp([x],[y]) values ('a',0)
insert into @temp([x],[y]) values ('a',0)
insert into @temp([x],[y]) values ('a',0)
insert into @temp([x],[y]) values ('a',1)
insert into @temp([x],[y]) values ('a',0)
insert into @temp([x],[y]) values ('a',0)
insert into @temp([x],[y]) values ('a',2)
insert into @temp([x],[y]) values ('a',3)
insert into @temp([x],[y]) values ('b',0)
insert into @temp([x],[y]) values ('b',1)
insert into @temp([x],[y]) values ('b',0)
insert into @temp([x],[y]) values ('b',0)
insert into @temp([x],[y]) values ('b',2)
insert into @temp([x],[y]) values ('b',3)
insert into @temp([x],[y]) values ('b',0)
insert into @temp([x],[y]) values ('b',0)

--select * from @temp 

DECLARE @int int=0
;WITH CTE as(
select *,1 as incr from @temp where row=1 
union all
select t.*,
CASE WHEN t.x=c.x then CASE WHEN t.y=c.y then incr else incr+1 end else CASE WHEN t.y=c.y then @int else @int+1 end end as incr
from @temp t inner join CTE c
on t.row=c.row+1
)

select * from CTE