title: T-SQL: Deleting all duplicate rows but keeping one
body: <p>I have a table with a very large amount of rows. Duplicates are not allowed but due to a problem with how the rows were created I know there are some duplicates in this table.
  I need to eliminate the extra rows from the perspective of the key columns. Some other columns may have <em>slightly</em> different data but I do not care about that. I still need to keep one of these rows however. SELECT DISTINCT won't work because it operates on all columns and I need to suppress duplicates based on the key columns.</p>
  
  <p>How can I delete the extra rows but still keep one efficiently?</p>