Regarding the table itself it may be synonymous, but when referencing a table with ''referencing tablename'' it will always and only refer to the primary key. Referencing anything only ''unique'' requires ''refererencing tablename(col1,col1)''.
Regarding the table itself it may be synonymous, but when referencing a table with ''referencing tablename'' it will always and only refer to the primary key. Referencing anything only ''unique'' requires ''refererencing tablename(col1,col1)''.