column options in sql

Hello, I got a question about sql. How can I create a column that values can not repeat, so there can be no identicall values in that column (just like a PK). Well I remember I can do this in MS Access by ticking one of the options, but in the sql I didn't see such an option.

You create a unique index on the column.

and how to do that in SQL studio please ?

I do it by code.

Create Unique Index Un_Table1FirstNameLastName on Person
(FirstName,LastName)

Or you can add a unique key constraint for that column during the creation of the table or alter the table and add the constraint