sql-group-如何在SQL查询中给组中的子组不同的行ID？

Question

i have bunch of discount scheme for my item table , and for each item i have different discount scheme. now i want to give row id to that item but it should be start from zer0(0) for each item group, and when it got different DiscountId then it should be change, my table is in below image..

now for an example, for ItemCode 429 there are 7 same discount with DiscountId 427 so for this all i want row Id 0(zero) but when change DiscountId, it means for Same ItemCode and 428 DiscountId, then i want another RowId with increment. and when ItemCode change then rowId should be start from Zero(0).

can anyone help me please??

my current query is simpaly "select * from ItemDiscount_md".

Answer 1

Maybe something like this:

Test data:

DECLARE @tbl TABLE(ITEMCode INT,DiscountId INT)
INSERT INTO @tbl
VALUES
(73,419),(73,419),(73,420),(73,420),(73,420),
(429,427),(429,427),(429,427),(429,427),(429,427),
(429,427),(429,427),(429,427),(429,428),(429,428)

Query:

;WITH CTE
AS
(
    SELECT
        DENSE_RANK() OVER(PARTITION BY tbl.ITEMCode 
                          ORDER BY DiscountId) AS Rownbr,
        tbl.*
    FROM
        @tbl AS tbl
)
SELECT
    CTE.Rownbr-1 AS RowNbr,
    CTE.DiscountId,
    CTE.ITEMCode
FROM
    CTE

Of course you can simplify the query by writing this:

SELECT
    (DENSE_RANK() OVER(PARTITION BY tbl.ITEMCode 
                       ORDER BY DiscountId))-1 AS Rownbr,
    tbl.*
FROM
    @tbl AS tbl

I just thought it was nicer and more readable with a CTE function

References:

• DENSE_RANK
• OVER Clause
• Using Common Table Expressions
• ROW_NUMBER

EDIT

To answer the comment. No ROW_NUMBER will not return the same counter. This is the output with DENSE_RANK :

0   419 73
0   419 73
1   420 73
1   420 73
1   420 73
0   427 429
0   427 429
0   427 429
0   427 429
0   427 429
0   427 429
0   427 429
0   427 429
1   428 429
1   428 429

And this is with ROW_NUMBER :

0   419 73
1   419 73
2   420 73
3   420 73
4   420 73
0   427 429
1   427 429
2   427 429
3   427 429
4   427 429
5   427 429
6   427 429
7   427 429
8   428 429
9   428 429

As you see ROW_NUMBER () recounts the group when the DENSE_RANK ranks the group

Answer 2

Just more simplified Arion's Answer

 DECLARE @tbl TABLE(ITEMCode INT,DiscountId INT)
INSERT INTO @tbl
VALUES
(73,419),
(73,419),
(73,420),
(73,420),
(73,420),
(429,427),
(429,427),
(429,427),
(429,427),
(429,427),
(429,427),
(429,427),
(429,427),
(429,428),
(429,428)

;
SELECT
    (DENSE_RANK() OVER(PARTITION BY ITEMCode ORDER BY DiscountId) -1) AS Rownbr,
    DiscountId,
    ITEMCode
FROM
    @tbl

Answer 3

if you got data like this: (from the image) @temp table

itemcode    DiscountId  DayId
----------- ----------- -----------
102         416         2
102         416         3
102         416         4
79          419         3
79          419         1
79          420         2
79          420         1

use row_number() to get below result

itemcode    DiscountId  DayId       rowid
----------- ----------- ----------- --------------------
102         416         2           1
102         416         3           2
102         416         4           3
79          419         3           1
79          419         1           2
79          420         2           1
79          420         1           2

SQL example:

select itemcode, DiscountId, DayId
, ROW_NUMBER() over (partition by Discountid order by discountid) as 'rowid'
from @temp