Delete Duplicate : Using internal storage key/Row Id

Posted: 03/09/2015 in Tips and Tricks
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When we think of delete duplicate, we are familiar with deleting data by generating row number for each row( either using derived table or CTE). Now here I would like to show you a method to identify each row from duplicated records without using row number or temp table logic.

The method would break down a concept of duplicate rows in SQL and this key word works after SQL2005. As I said there is no duplicate rows in SQL, even the rows are duplicated each rows are stored identically and they can be identified using an internal storage id called Row Id. Let us see how to utilize this id to resolve our issue.

physloc

Above I have created a table and inserted duplicated rows, in the select query I have used “%%Physiloc%%” keyword and displays row id of each rows (this is an hexadecimal value of the location where rows are being stored), we can use this row ID to delete duplicate rows from the table using very simple logic.

physloc2

Here I have deleted the duplicate rows only by executing the first query in the above screenshot.

Take away : There is no duplicate rows in a table, each rows can be identified by Row ID of each row. Please do leave your comments, we will discuss more about physiloc in up coming post.

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