Database Reference
In-Depth Information
Meaning of minimum cardinality indicator 0
Some department entities may
not be associated with any employee entities. Not every department entity is
associated with employee entities. That is, the minimum number of employee
instances associated with one department entity is 0. Not every department
entity participates in the relationship. Note the dotted or broken relationship
line next to the DEPARTMENT entity type, indicating that the relationship
on this side is optional and that not every department entity participates in
the relationship. A broken or dotted line denotes partial participation in the
relationship.
Meaning of maximum cardinality indicator *
A department entity may be asso-
ciated with many employee entities.
An employee must be assigned to at least one department, and he or she can
be assigned to only one department.
Note minimum cardinality indicator 1 and
maximum cardinality indicator 1 near DEPARTMENT entity type.
Meaning of minimum cardinality indicator 1
Each employee entity is asso-
ciated with at least one department entity. That is, the minimum number of de-
partment instances associated with one employee entity is 1. Note the solid
relationship line next to EMPLOYEE, indicating that the relationship on
this side is mandatory and that every employee entity participates in the
relationship.
Meaning of maximum cardinality indicator 1
An employee entity can be asso-
ciated with one instance of department at most.
Case 4
Every department may not have employees; if a department has employees, it can
have many employees.
Note minimum cardinality indicator 0 and maximum car-
dinality indicator * near EMPLOYEE entity type.
Meaning of minimum cardinality indicator 0
Some department entities may not
be associated with any employee entities. Not every department entity is associ-
ated with employee entities. That is, the minimum number of employee instances
associated with one department entity is 0. Not every department entity par-
ticipates in the relationship. Note the dotted or broken relationship line next
to DEPARTMENT entity type, indicating that the relationship on this side is
optional and that not every department entity participates in the relationship. A
broken or dotted line denotes partial participation in the relationship.
Every employee may not be assigned to a department; if assigned, he or she can
be assigned to only one department.
Note minimum cardinality indicator 0 and
maximum cardinality indicator 1 near DEPARTMENT entity type.
Meaning of minimum cardinality indicator 0
Some employee entities may not
be associated with any department entities. Not every employee entity is asso-
ciated with a department entity. That is, the minimum number of department
instances associated with one employee entity is 0. Not every employee entity
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