How to remove duplicate records from history table to join to another table in SQL server

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I have a table with orders and need to join unique records from history table could you please assist on how to get unique records by create date

order_id  itemname  hierarchyid  Createddate
1         Keyboard  4000         12/11/2017
2         Mouse     3000         12/11/2016
3         Monitor   1200         12/11/2015
4         Keyboard  4000         12/11/2014
5         Mousepad  3000         12/11/2013
1         Monitor   1200         12/11/2012
2         Keyboard  4000         12/11/2011
5         Mousepad  3000         12/11/2010

;with cte as (select distinct order_id ,hierarchyid, itemname, Createddate from orders order by createdate)
Select * from cte

What I have tried:

I have tried to get unique records with the below cte but not able to distinct records

order_id  itemname  hierarchyid  Createddate
1         Keyboard  4000         12/11/2017
2         Mouse     3000         12/11/2016
3         Monitor   1200         12/11/2015
4         Keyboard  4000         12/11/2014
5         Mousepad  3000         12/11/2013
1         Monitor   1200         12/11/2012
2         Keyboard  4000         12/11/2011
5         Mousepad  3000         12/11/2010


;with cte as (select distinct order_id ,hierarchyid, itemname, Createddate from orders order by createdate)
Select * from cte

Expected result should be like below

order_id  itemname  hierarchyid  Createddate
1         Keyboard  4000         12/11/2017
2         Mouse     3000         12/11/2016
3         Monitor   1200         12/11/2015
4         Keyboard  4000         12/11/2014
5         Mousepad  3000         12/11/2013

Posted 25-Mar-24 8:11am

Ganesh Kumar 2024

Updated 25-Mar-24 8:25am

PIEBALDconsult

v2

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Comments

PIEBALDconsult 25-Mar-24 14:28pm

0) I think it's doing exactly what you told it to do.
1) Avoid using DISTINCT.
2) Don't put the ORDER BY in the CTE.

Ganesh Kumar 2024 25-Mar-24 14:41pm

here not to get duplicate records which are repeated and need to get only last update single records only

2 solutions

Solution 1

You should Group By the first three columns in your results and use Max() of your last column. That should get you what I think you want.

Select order_id, itemname, hierarchyid, Max(Createddate) as LastOrderDate
From orders
Group By order_id, itemname, hierarchyid
Order By Createddate desc

Posted 25-Mar-24 10:30am

kmoorevs

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Richard Deeming · Accepted Answer · 2024-03-25T22:58:00

Based on your expected output, you don't want "distinct" records; you want the last record for each order ID.

SQL

WITH cte As 
(
    SELECT
        order_id,
        hierarchyid, 
        itemname, 
        Createddate,
        ROW_NUMBER() OVER (PARTITION BY order_id ORDER BY Createddate DESC) As RN
    FROM
        orders
)
SELECT
    order_id,
    hierarchyid, 
    itemname, 
    Createddate
FROM
    cte
WHERE
    RN = 1
;

ROW_NUMBER (Transact-SQL) - SQL Server | Microsoft Learn[^]

NB: If two orders have the same Createddate, then this will pick one at random. You should either add an additional "tie-breaking" sort condition to the ROW_NUMBER; or, if you want to return all rows for the latest order, switch to using the RANK function[^] instead.