title: SQL Remove non duplicate entires in a table
body: <p>I have a table with two columns <code>CountryCode CountryName</code>. There are duplicate entries in <code>countrycode</code>. But I want to remove the non-duplicate entires and keep the rows which are duplicates in the <code>countrycode</code> column. So I am trying to write an SQL statement to do this. I think I have to use Having but not too sure how exactly to incorporate it. Thanks</p>