yogi_Filter An Imported Sheet To ONLY Display Rows With Duplicate Entries (First And Last Names Combined)

                                        Google Spreadsheet   Post  #1683
Yogi Anand, D.Eng, P.E.      ANAND Enterprises LLC -- Rochester Hills MI     www.energyefficientbuild.com.   Jun-28-2014
post by Regional Command: (https://productforums.google.com/forum/#!searchin/docs/C1$3AS1000/docs/FlXCIELSbdY/bOnvZzZjICYJ)
Filter an imported sheet to ONLY display rows with duplicate columns

Hello,

I have used the following formula to import data from another spreadsheet:

=Query(importRange("THE_KEY", "Form Responses!C1:S1000"), "select Col1, Col2, Col3, Col4, Col5, Col6, Col7, Col8, Col9, Col10, Col11, Col12, Col13, Col14, Col15, Col16, Col17",1)

I would like to know how to alter this to ONLY display data that has duplicate values in Col1 and Col2. Col1 is "First Name" and Col2 is "Last Name" and this is a registration sheet so basically, I want to create a filter to determine who has registered more than once so I may delete their duplicate records. Thanks!

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