Min time stamp partition by same value in column-CodePudding

I have a below dataset where I'm trying to get the min timestamp of the same values in a single column.

Here is my dataset.

I am trying to create a column to find user_first_comment for each interaction with dealer.

like below

is there any technique that i can use to add a incremental value for same values in columns. for example column RANK_Incremental,so that i can use Min wit hpartition to get final output.

CodePudding user response：

With common table expressions (or derived tables) and window function support, try the following:

WITH step1 AS (
        SELECT *, CASE WHEN LAG(note_type) OVER (PARTITION BY incident ORDER BY note_date) = note_type THEN 0 ELSE 1 END AS edge FROM incidents
     )
   , step2 AS (
        SELECT *, SUM(edge) OVER (PARTITION BY incident ORDER BY note_date) AS grp FROM step1
     )
SELECT *, FIRST_VALUE(note_date) OVER (PARTITION BY incident, grp ORDER BY note_date) AS first_date FROM step2
;

The result:

 ---------- --------------------- ---------------- ------ ------ --------------------- 
| incident | note_date           | note_type      | edge | grp  | first_date          |
 ---------- --------------------- ---------------- ------ ------ --------------------- 
|  5498091 | 2021-12-15 17:20:00 | USER_COMMENT   |    1 |    1 | 2021-12-15 17:20:00 |
|  5498091 | 2021-12-15 17:21:00 | USER_COMMENT   |    0 |    1 | 2021-12-15 17:20:00 |
|  5498091 | 2021-12-15 17:55:00 | DEALER_COMMENT |    1 |    2 | 2021-12-15 17:55:00 |
|  5498091 | 2021-12-15 17:59:00 | USER_COMMENT   |    1 |    3 | 2021-12-15 17:59:00 |
|  5498091 | 2021-12-16 11:02:00 | USER_COMMENT   |    0 |    3 | 2021-12-15 17:59:00 |
|  5498091 | 2021-12-16 16:46:00 | DEALER_COMMENT |    1 |    4 | 2021-12-16 16:46:00 |
 ---------- --------------------- ---------------- ------ ------ ---------------------

The setup:

CREATE TABLE incidents (
   incident         int
 , note_date        datetime
 , note_type        varchar(20)
)
;

INSERT INTO incidents VALUES
   (5498091, '2021-12-15 17:20', 'USER_COMMENT')
 , (5498091, '2021-12-15 17:21', 'USER_COMMENT')
 , (5498091, '2021-12-15 17:55', 'DEALER_COMMENT')
 , (5498091, '2021-12-15 17:59', 'USER_COMMENT')
 , (5498091, '2021-12-16 11:02', 'USER_COMMENT')
 , (5498091, '2021-12-16 16:46', 'DEALER_COMMENT')
;