Database Reference
In-Depth Information
In the table CLASS, more speciic information about a class is added to the table. We did not
add the information in Table 3.1 earlier so that we can focus on the normalization process.
As mentioned earlier that a table has no transitive dependency if each nonkey column
(except the foreign key column) directly depends on the primary key. Although we still have
StudentName
→
FacultyID in the STUDENT table, FacultyID is a foreign key. herefore, there
is no transitive dependency. Now, the table STUDENT_CLASS is broken up into three tables
STUDENT, STUDENT_CLASS, and CLASS as shown in Tables 3.7 through 3.9.
In the STUDENT table, the determinant StudentName is now a candidate key. herefore,
the table STUDENT is in the BCNF. By the same argument, the tables STUDENT_CLASS and
CLASS are in the BCNF. Also, the size of the above tables has been signiicantly reduced.
Tables in BCNF can still have other types of dependencies that cause modiication anomalies.
he next level normal form is 4NF, which will be discussed in the following:
Fourth normal form
: Being in 4NF, a table should be in the BCNF and should not have
multivalue dependency
.
Multivalue dependency
is diferent from functional dependency. To
illustrate the multivalue dependency, let us consider the following tables.
Table 3.7
STUDENT Table
StudentID
StudentName
FacultyID
10
Liz
1
11
Joe
2
12
Linda
1
13
Don
3
14
Jan
4
16
Bruce
3
Table 3.8
STUDENT_CLASS Table
StudentID
ClassID
Grade
10
1000
A
11
1001
C
12
1002
B
13
1000
C
14
1001
B
10
1003
A
16
1004
B
11
1006
B
13
1005
A
