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This article mainly introduces "the method of deleting duplicate data in the database". In the daily operation, I believe that many people have doubts about the method of deleting duplicate data in the database. The editor consulted all kinds of data and sorted out the simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts about "the method of deleting duplicate data in the database". Next, please follow the editor to study!

Method 1: declare@maxinteger,@idinteger declarecur_rowscursorlocalforselect main field, count (*) from table name groupby main field havingcount (*) > 1 opencur_rows fetchcur_rowsinto@id,@max while@@fetch_status=0 begin select@max=@max-1 setrowcount@max deletefrom table name where main field = @ id fetchcur_rowsinto@id,@max end closecur_rows setrowcount0 method 2 there are two duplicate records, one is a completely duplicate record, that is, a record in which all fields are duplicated Second, some records with duplicate key fields, such as duplicate Name fields, while other fields are not necessarily duplicated or can be ignored.

1. For the first kind of repetition, it is relatively easy to solve, and the result set without duplicate records can be obtained by using selectdistinct*fromtableName. If the table needs to delete duplicate records (keep 1 duplicate record), you can delete selectdistinct*into#TmpfromtableName droptabletableName select*intotableNamefrom#Tmp droptable#Tmp as follows. The reason for this repetition is due to poor table design, which can be solved by adding a unique index column. 2. This kind of duplicate problem usually requires the retention of the first record in the duplicate record. The operation method is as follows: suppose the duplicate field is Name,Address, and the result set selectidentity (int,1,1) asautoID,*into#TmpfromtableName selectmin (autoID) asautoIDinto#Tmp2from#TmpgroupbyName,autoID select*from#TmpwhereautoIDin (selectautoIDfrom#tmp2) which is unique to these two fields is required. The last select is the result set that Name,Address does not repeat (but there is an extra autoID field. When actually writing, you can omit this column in the select clause)

At this point, the study on "the method of deleting duplicate data in the database" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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