SQL Server 2008中的递归查询

Question

I have this table

MyTable

rowNew  rowOld

1 ------- 2

2 ------- 3

3 ------- 4

4 ------- 5

7 ------- 8

8 ------- 9

I want to select query like this:

rowNew  rowOld

1 ------- 2

2 ------- 3

3 ------- 4

4 ------- 5

i wrote this with cte

with cte(rowNew, rowOld)
as
(
select rowNew, rowOld from MyTable
union all
select rowNew, rowOld from MyTable
inner join cte on MyTable.rowOld = cte.rowNew
)
select rowNew, rowOld from cte
where cte.rowNew = 1

and I got this records:

rowNew  rowOld

1 ------- 2

1 ------- 2

1 ------- 2

1 ------- 2

what is he problem?

Answer 1

You put your where condition in the wrong spot - it should be in the anchor query in the CTE definition to limit your starting point.

Also, you have join condition the other way round if you want to define parent-child relationship.

It all should be:

with cte(rowNew, rowOld)
as
(
select rowNew, rowOld from MyTable
where rowNew = 1
union all
select MyTable.rowNew, MyTable.rowOld from MyTable
inner join cte on MyTable.rowNew = cte.rowOld
)
select rowNew, rowOld from cte

SQL Fiddle demo