Detecting Duplicates

On 30 Apr, 2015

T-SQL

By : Dave Jenkins

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There are many ways of detecting duplicate data in your tables. One of the quick and easiest methods I have found is to use the below syntax.

It will return a list of duplicate entries by the field that you’ve chosen and the number of duplications. This then allows you to use that list in a subsequent query to return all of the data within the duplicate row. From there you can then make a decision about what you want to do with the duplicate data.

SELECT		EmployeeID, COUNT(*)
FROM		#testTable
GROUP BY	EmployeeID
HAVING		COUNT(*) > 1;
GO

SELECT EmployeeID, COUNT(*)

FROM #testTable

GROUP BY EmployeeID

HAVING COUNT(*) > 1;

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About The Author

Dave Jenkins

Hello! I'm Dave Jenkins and I have been working with MS SQL Server for two years. I'm an MCP (70-461) working towards an MCSA. I love working with MS SQL Server and the BI Stack.

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