How to Find and Retrieve Duplicate Rows and Their IDs in SQL Server?

Retrieving Duplicate Rows and Associated IDs in SQL Server

Eliminating duplicate rows from a database is crucial for data integrity and efficiency. In this scenario, we aim to identify and retrieve all duplicate rows from an organizations table, along with their corresponding IDs and the count of duplicated rows.

To achieve this, we can leverage SQL Server's powerful capabilities. The provided statement effectively identifies duplicate rows and provides a count of duplications:

SELECT orgName, COUNT(*) AS dupes
FROM organizations
GROUP BY orgName
HAVING COUNT(*) > 1

To enhance this query, we can introduce a subquery that generates a table of distinct organization names and corresponding dupe counts:

SELECT orgName, COUNT(*) AS dupeCount
FROM organizations
GROUP BY orgName
HAVING COUNT(*) > 1

This subquery is then joined with the main organizations table using the orgName column, allowing us to retrieve the IDs associated with each duplicate row:

select o.orgName, oc.dupeCount, o.id
from organizations o
inner join (
    SELECT orgName, COUNT(*) AS dupeCount
    FROM organizations
    GROUP BY orgName
    HAVING COUNT(*) > 1
) oc on o.orgName = oc.orgName

This refined query now provides a comprehensive list of duplicate organization rows, their associated IDs, and the count of duplications. This information empowers you to manually merge duplicate rows safely, ensuring data integrity while maintaining relationships with other tables in your database.

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