Question

i use sql to delete duplicate record but it is not working. can anyone help me.

my sql is

delete from VehicleInfoForParts where
Stock_Code not in
(
select max(Stock_Code) from VehicleInfoForParts group by stock_code,makeid,modelid
)

thanks

Answer 1

If you’re on SQL SErver 2005 and up, you can use a CTE (Common Table Expression) do achieve this:

;WITH DupData AS
(
    SELECT Stock_Code, MakeID, ModelID,
        ROW_NUMBER() OVER(PARTITION BY stock_code,makeid,modelid ORDER BY Stock_Code DESC) 'RowNum'
    FROM
        dbo.VehicleInfoForParts 
)
DELETE FROM DupData
WHERE RowNum > 1

Basically, the SELECT statement inside the CTE groups your data by (stock_code, makeid, modelid) – i.e. each “group” of those three elements gets a consecutive row_number starting at one. The data is sorted by stock_code descending, so the largest number is the first one, the one with RowNum = 1 – so anything else (with a RowNum > 1) is a duplicate and can be deleted.