Technical data

Figure 5–8 Set Relationships
PART VENDOR
VENDOR_SUPPLY
SUPPLY
ZK−1486−GE
PART_SUPPLY
Figure 5–9 Occurrence Diagram of a Relationship Between Two Set Types
ZK−1487−GE
PART_SUPPLY VENDOR_SUPPLY
U.S. SEALS
EASTERN GASKETS
SEAL−TITE
GASKET
500
100
750
5.9.1 Simple Set Relationships
A simple set relationship contains one owner record type and one or more
member record types. Simple relationships are used to represent a basic one-to-
many relationship where one owner record occurrence owns zero, one, or several
member record occurrences. Simple relationships are created with a single set
type. There are three kinds of sets in simple relationships: system-owned sets,
simple sets, and forked sets.
5.9.1.1 System-Owned Sets
By definition, a set contains one owner record and may contain zero or more
member records. Sets owned by the system, however, have only one occurrence in
the database and are called system-owned sets. System-owned sets are used as
entry points into the database. You cannot access the owner of a system-owned
set (the system), but you can access its member records. System-owned sets are
also called singular sets. Figure 5–10 is an example of a system-owned set type.
Database Programming with HP COBOL 5–11