Delete Duplicate Rows in SQL Server

In this article we will show you, How to write a SQL Query to Delete Duplicate Rows in SQL Server with example. This is one of the common SQL Interview Question that you might face in the interviews. For this example, We are going to use the below shown data (few columns from Fact Internet Sales in Adventure Works DW)

SQL CODE

In order to keep the example as simple as possible, we created a new table, and then inserted the above data into new table

SQL CODE

Below screenshot will show you the data that we inserted into the DupFactInternetSales table present in the SQL Tutorial database.

Let me show you the unique records present in the table. As you can see, we used the SELECT DISTINCT keyword

Delete Duplicate Rows in SQL Server Example 1

In this example we will show you, How to delete Duplicate rows in SQL Server using the ROW_NUMBER function, and the Common Table Expression.

T-SQL CODE

Within the CTE, we are using the Rank function called ROW_NUMBER. This will assign unique rank number from 1 to n. Next, we are deleting all the records, whose rank number is greater than 1.

OUTPUT: Let me show you the output of the statement

OUTPUT

Let us see the data present in the DupFactInternetsales, after the Delete Operation

Delete Duplicate Rows in SQL Server Example 2

In this example we will show you, How to remove Duplicate rows in SQL Server using the SELF JOIN.

T-SQL CODE

OUTPUT: Let me show you the output of the statement

OUTPUT

Delete Duplicate Rows in SQL Server Example 3

In this example we will show you, How to delete Duplicate rows in SQL Server using the LEFT JOIN, MIN Function, GROUP BY, and HAVING.

T-SQL CODE

OUTPUT: Let me show you the output of the statement

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