SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 

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.

DMCA.com

Vivek's SQL Notes

Vivek johari is currently a Analyst and have more that 5.5 yeras of experience in database. He has Master degree in Computer and also he is Microsoft certified Sql DBA (MCTS)& Microsoft certified SQl BI professional(MCTS). He is also Oracle certified profession(OCP)DBA in ORACLE 10g and ORACLE 9i.He has the experience of working in PL/SQL, T-SQL and SSIS/SSRS. His work basically involved designing and optimization of the Database.He has also published many database articles on his blog Technologies with Vivek Johari.

Comments

Leave a comment on the original post [feedproxy.google.com, opens in a new window]

Loading comments...