Have you ever combined several spreadsheets but needed to get rid of the duplicates?  If you have thousands of rows to go through this can take a while.  The solution is simple:

Let us say you have a spreadsheet with Column "A" containing a Part Number.  The rest of the columns have descriptions, prices, etc.
Insert a column between "A" and "B" which then becomes "B"
Enter the following formula into the newly created column "B" at the top line 1. or line 2 if you have a header.

=If(COUNTIF($A$1:A1,A1)>1,"Dup","")

or if you have a header then change the formula to this

=If(COUNTIF($A$2:A2,A2)>1,"Dup","")

Next you must  highlight the formula and highlight the rest of the column to the bottom of  the spreadsheet and  fill down  (Ctrl-D) the formula.
Where ever  it finds a duplicate it will put in the word  Dup and you can sort this column  so that all the Dups  are together then easily delete or copy the rows as you see fit.