How to delete completely duplicate rows

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) Valu         


        

Answer 1

First use a SELECT... INTO:

SELECT DISTINCT ProductID, ProductName, Description, Category
    INTO tblProductClean
    FROM tblProduct

The drop the first table.

Answer 2

DELETE tblProduct 
FROM tblProduct 
LEFT OUTER JOIN (
   SELECT MIN(ProductId) as ProductId, ProductName, Description, Category
   FROM tblProduct 
   GROUP BY ProductName, Description, Category
) as KeepRows ON
   tblProduct.ProductId= KeepRows.ProductId
WHERE
   KeepRows.ProductId IS NULL

Stolen from How can I remove duplicate rows?

UPDATE:

This will only work if ProductId is a Primary Key (which it is not). You are better off using @marc_s' method, but I'll leave this up in case someone using a PK comes across this post.

Answer 3

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

Answer 4

I had to do this a few weeks back... what version of SQL Server are you using? In SQL Server 2005 and up, you can use Row_Number as part of your select, and only select where Row_Number is 1. I forget the exact syntax, but it's well documented... something along the lines of:

Select t0.ProductID, 
       t0.ProductName, 
       t0.Description, 
       t0.Category
Into   tblCleanData
From   (
    Select ProductID, 
           ProductName, 
           Description, 
           Category, 
           Row_Number() Over (
               Partition By ProductID, 
                            ProductName, 
                            Description, 
                            Category
               Order By     ProductID,
                            ProductName,
                            Description,
                            Category
           ) As RowNumber
    From   MyTable
) As t0
Where t0.RowNumber = 1

Check out http://msdn.microsoft.com/en-us/library/ms186734.aspx, that should get you going in the right direction.