In this tutorial we have discussed and shown displayed step by step method to select ad delete duplicate records using SQL. Anyone can easily follow through and master this method for using it for databases dealing with a huge array of data.
In order to find duplicate records and count them we can use “group_by” and “COUNT” clause.
SELECT
FirstName,
LastName,
COUNT(*) AS Count
FROM Customers
GROUP BY FirstName, LastName
HAVING COUNT(*) > 1;
Now if few customers have identical first names and last names then we will exactly know how many are they. To delete them we need to use this query.
DELETE d1 FROM Dogs d1
INNER JOIN Dogs d2
WHERE
d1.DogId < d2.DogId AND
d1.FirstName = d2.FirstName AND
d1.LastName = d2.LastName;
If you have any questions then write down in comments section please.