What is a Primary Key? Why is it important? when is it necessary for the primary key to include multiple fields? Additional Content? You can add text and files that support your answers. When sorting data on more than one field in an access query, which field is the major sort key? Which field is the minor sort key? What effects do these keys have on the order in which the rows are displayed? Additional Content? You can add text and files that support your answers. Describe the purpose of the following commands in relational algebra: SELECT PROJECT JOIN UNION INTERSECT SUBTRACT Additional Content? You can add text and files that support your answers