SQL SYntext For checking of Duplicates in an excel sheet

Hi there, i have a problem of finding the correct SQL syntext for checking
for duplicates in an excel sheet.
Anyone out here can point out to me the keyword to use or syntext?
Wht i need to do is to checks for duplicates in the excel sheet and when
duplicates are found , skips them and move on to the next row .



Thx!
Faizal