Insert values into temp Table with Partition By

Question

If have a temporary table declared as following:

CREATE TABLE #tempKleerkast(
id INT IDENTITY NOT NULL PRIMARY KEY,
IDKleerkastPersoon int,
ID_Persoon int,
rk int
)

Now i wish to fill up the table with the values from an actual table where i want to get the latest (Not Max) record for each person. Therefor i'm using the following query:

      SELECT 
      DISTINCT IDKleerkastPersoon AS Expr1, kk.ID_Persoon,
      ROW_NUMBER() OVER (PARTITION BY kk.ID_Persoon
                            ORDER BY kk.IDKleerkastPersoon DESC) AS rk
      FROM KleerkastPerPersoon kk
      WHERE  kk.ID_Persoon IS NOT NULL AND rk = 1

The problem is where is when i wish to use insert into as following:

      INSERT INTO #tempKleerkast(IDKleerkastPersoon,ID_Persoon,rk)
      SELECT 
      DISTINCT IDKleerkastPersoon AS Expr1, kk.ID_Persoon,
      ROW_NUMBER() OVER (PARTITION BY kk.ID_Persoon
                            ORDER BY kk.IDKleerkastPersoon DESC) AS rk
      FROM KleerkastPerPersoon kk
      WHERE  kk.ID_Persoon IS NOT NULL AND rk = 1

I get the following error: Invalid column name 'rk'. Any idea why he doesn't recognise the column rk?

Note: The column rk is needed further on in the stored procedure. So i can't exclude it.

Answer 1

No, the problem comes before you write the INSERT. Try running just the plain SELECT and you'll see exactly the same error. Logically, WHERE runs before SELECT so you can't refer to aliases introduced by the latter in the former.

This should work:

  INSERT INTO #tempKleerkast(IDKleerkastPersoon,ID_Persoon,rk)
  SELECT IDKleerkastPersoon, ID_Persoon, rk
  FROM (
     SELECT
       IDKleerkastPersoon, kk.ID_Persoon,
          ROW_NUMBER() OVER (PARTITION BY kk.ID_Persoon
                        ORDER BY kk.IDKleerkastPersoon DESC) AS rk
     FROM KleerkastPerPersoon kk
     WHERE  kk.ID_Persoon IS NOT NULL) t
  WHERE rk = 1

(I also removed the DISTINCT since one of the columns listed was also a column listed in the PARTITION BY clause and we're only selecting one row from each partition)