"StackOverflow problem Selection" in SQL to remove duplicate rows

problemSuppose you have a table with a larger amount of data (for example, 300,000+ rows), where there are duplicate rows (other than the primary key, the other column data is the same), how do you quickly go heavy? My watch looks like this.

MyTable-----------RowID int not null identity(1,1) primary key,Col1 varchar(20) not null,Col2 varchar(2048) not null,Col3 tinyint not null

Essence AnswerAssuming there are no null values, you can first group by the other columns, and then only Min or Max (RowId), to delete the other rows:

DELETE MyTable FROM MyTableLEFT OUTER JOIN (   SELECT MIN(RowId) as RowId, Col1, Col2, Col3    FROM MyTable    GROUP BY Col1, Col2, Col3) as KeepRows ON   MyTable.RowId = KeepRows.RowIdWHERE   KeepRows.RowId IS NULL

If ROWID is not of type int, but is a GUID, you can use the

StackOverflow Link: http://stackoverflow.com/questions/18932/how-can-i-remove-duplicate-rows

"StackOverflow problem Selection" in SQL to remove duplicate rows