You need to read a book (
any book!) or refer number of tutorials on web...
There is a difference between unique key and primary key.
MSDN: Primary key Constraints[
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MSDN: Unique Key Constraints[
^]
After creating a table, you define the columns. There is a property window associated with a column created, use that for setting various properties/constraints for that column. There is a right click option too for setting selected constraints.