? Table does not support this operation because it is not uniquely indexed ?

Though I think I know what that message means, what does it have to do with
trying to open a query with a SQL statement that is trying to collect all
the records that below to a particular student?

The Primary Key of the file is SSN, Test_Type, Test_Date. The SQL I'm using in
the query/view is "select * from Tests where SSN='##...'" The SSN field would
be a sub-key to the primary key. How do I get around this?