Question

Say i have duplicate rows in my table and well my database design is of 3rd class :-

Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (1,'Cinthol','cosmetic soap','soap');
Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (1,'Cinthol','cosmetic soap','soap');
Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (1,'Cinthol','cosmetic soap','soap');
Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (1,'Lux','cosmetic soap','soap');
Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (1,'Crowning Glory','cosmetic soap','soap');
Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (2,'Cinthol','nice soap','soap');
Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (3,'Lux','nice soap','soap');
Insert Into tblProduct (ProductId,ProductName,Description,Category) Values (3,'Lux','nice soap','soap');

I want only 1 instance of each row should be present in my table. Thus 2nd, 3rd and last row whcih are completely identical should be deleted. What query can i write for this? Can it be done without creating temp tables? Just in one single query?

Thanks in advance 🙂

Answer 1

Try this – it will delete all duplicates from your table:

;WITH duplicates AS
(
    SELECT 
       ProductID, ProductName, Description, Category,
       ROW_NUMBER() OVER (PARTITION BY ProductID, ProductName
                          ORDER BY ProductID) 'RowNum'
    FROM dbo.tblProduct
)
DELETE FROM duplicates
WHERE RowNum > 1
GO

SELECT * FROM dbo.tblProduct
GO

Your duplicates should be gone now: output is:

ProductID   ProductName   DESCRIPTION        Category
   1          Cinthol         cosmetic soap      soap
   1          Lux             cosmetic soap      soap
   1          Crowning Glory  cosmetic soap      soap
   2          Cinthol         nice soap          soap
   3          Lux             nice soap          soap