DENSE_RANK() without duplication

Question

Here\'s what my data looks like:

| col1 | col2 | denserank | whatiwant |
|------|------|-----------|-----------|
| 1    | 1    | 1         | 1         |
| 2          


        

Answer 1

I think this is possible in pure SQL using some gaps and islands tricks, but the path of least resistance might be to use a session variable combined with LAG() to keep track of when your computed dense rank changes value. In the query below, I use @a to keep track of the change in the dense rank, and when it changes this variable is incremented by 1.

DECLARE @a int
SET @a = 1
SELECT t.col1,
       t.col2,
       t.denserank,
       @a = CASE WHEN LAG(t.denserank, 1, 1) OVER (ORDER BY t.col1) = t.denserank
                 THEN @a
                 ELSE @a+1 END AS [whatiwant]
FROM
(
    SELECT col1, col2, DENSE_RANK() OVER (ORDER BY COL2) AS [denserank]
    FROM [table1]
) t
ORDER BY t.col1