Method One: Take advantage of cursors, but be aware of the main field or identity column
Declare @max integer,@id integerDeclareCur_rowscursorLocal for SelectMain field,Count(*) fromTable nameGroup byMain field having Count(*)> 1Opencur_rowsFetchCur_rows into @id,@max while @ @fetch_status=0beginSelect @max = @max -1Set RowCount @maxDelete fromTable namewhereMain field= @idFetchCur_rows into @id,@maxEndClosecur_rowsSet RowCount 0
Method two: Using Temporal table processing
Method Two
There are two meanings of duplicate records, one is a completely duplicate record, that is, all fields are duplicated records, and the second is some key field duplicate records, such as the Name field repeats, and other fields may not be repeated or can be ignored.
1, for the first kind of repetition, easier to solve, using
SELECT DISTINCT * from TableName |
You can get a result set with no duplicate records.
If the table needs to delete duplicate records (duplicate records retain 1), you can delete them as follows
SELECT DISTINCT * to #Tmp from TableName drop table TableName SELECT * Into TableName from #Tmp drop table #Tmp |
This duplication occurs because the table is poorly designed and the unique index columns are added to resolve.
2, this kind of repetition problem usually requires to keep the first record in the duplicate record, the operation method is as follows
Suppose there is a duplicate field name,address, which requires the result set to be unique for both fields
Select Identity (int,1,1) as Autoid, * into #Tmp from TableName Select min (autoid) as autoid into #Tmp2 from #Tmp Group by name,autoid SELECT * from #Tmp where autoid on (select Autoid from #tmp2) |
The last select is the result set that name,address not duplicate (but one more autoid field, which can be written in the SELECT clause without this column in the actual write)
Deleting duplicate data in a table in SQL Server