How to prevent duplicate rows in list

Occasional Contributor

Hi, 

I would ask, if there ist a way how to avoid duplicate items in list? Not depends on only one column, but I need it for two and more columns.

Example: 
Col1 | Col2 | Col3
a      |    b   |  c -> OK
a      |    c   |  c -> OK
a      |    c   |  b -> OK
a      |    b  |   c -> Duplication - not OK. 

Thanks for any advice. 

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