Deleting Duplicate rows using CTE

Deleting Duplicate rows using CTE

Many times we caught in a situation where we have a table where there is no primary or unique column defined in it and rows with duplicate data inserted in the table. In this example I will tries to show how to delete the duplicate rows using CTE.

Suppose we have a table name “tbl_dublicatedata” whose table creation script is given below:-

Create table tbl_dublicatedata (name nvarchar(100), age int, salary int)

Now we insert duplicate data into this table. Insert script for these rows are given below:-

Insert  into tbl_dublicatedata
select ‘Vivek’, 28, 800000
union all
select ‘Avinash’, 29, 600000
union all
select ‘Vivek’, 28, 800000

If we want to see the data into the table , we can run the following query

select * from  tbl_dublicatedata

This query will return the following result

With the help of the CTE we can remove these duplicate records.

With cte_duplicate (name, age, salary, rownumber)
as (
select name,age,salary, row_number()over(partition by name, age , salary order by name, age , salary)as rank from tbl_dublicatedata
)
delete from cte_duplicate where rownumber<>1

If we again see the data in the table tbl_dublicatedata using the same query which we used earlier we will get the following result:-

select * from  tbl_dublicatedata

From the result we can see that the duplicate rows are deleted and there is no duplicate data in the table.

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About vivekjohari

Database Consultant with more than 11.5 years of experience in database designing & programming and DBA related activities.  Had good experience on different databases like SQL Server, MySQL & Oracle, Azure SQL &  Big Data.
This entry was posted in Interview Questions, SQL Advanced, SQL CTE, SQL Server and tagged . Bookmark the permalink.

26 Responses to Deleting Duplicate rows using CTE

  1. Anonymous says:

    The “where” clause in the CTE delete is wrong, the field is called “rank” inside the cte but in the where is used “rownumber”

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