The Relational Model and Normalization - Database Processing: Fundamentals, Design, and Implementation - page 148

In each case, the determinant is associated with a set of values, and example data for each
of these multivalued dependencies are shown in Figure 3-28. Such expressions are read as
“EmployeeName multidetermines EmployeeDegree” and “EmployeeName multidetermines
EmployeeSibling” and “PartKitName multidetermines Part.” Note that multideterminants are
shown with a double arrow rather than a single arrow.
Employee Jones, for example, has degrees AA and BS. Employee Greene has degrees BS,
MS, and PhD. Employee Chau has just one degree, BS. Similarly, employee Jones has siblings
(brothers and sisters) Fred, Sally, and Frank. Employee Greene has sibling Nikki, and employee
Chau has siblings Jonathan and Eileen. Finally, PartKitName Bike Repair has parts Wrench,
Screwdriver, and Tube Fix. Other kits have parts as shown in Figure 3-28.
Unlike functional dependencies, the determinant of a multivalued dependency can never
be the primary key. In all three of the tables in Figure 3-28, the primary key consists of the
composite of the two columns in each table. For example, the primary key of the EMPLOYEE_
DEGREE table is the composite key (EmployeeName, EmployeeDegree).
Multivalued dependencies pose no problem as long as they exist in tables of their own.
None of the tables in Figure 3-28 has modification anomalies. However, if A S S B, then
any relation that contains A, B, and one or more additional columns will have modification
anomalies.

EMPLOYEE_DEGREE

Figure 3-28
three Examples of
Multivalued Dependencies

EMPLOYEE_SIBLING

PARTKIT_PART