Technical data

Figure 5–15 Many-to-Many Relationship Between Two Types of Records
ZK−1493−GE
VENDOR RECORD TYPE
PART RECORD TYPE
SUPPLY RECORD TYPE
PART_SUPPLY SET VENDOR_SUPPLY SET
1−WEEK 5−DAYS
1−MONTH
2−DAYS
SOUND−OFF CO
Musico, Inc.
CASSETTE
TAPE
5.9.2.2 Many-to-Many Relationships Between Records of the Same Type
To represent a relationship between record occurrences of the same type, the DBA
builds a many-to-many relationship using member records to create the necessary
links. Figure 5–16 shows a many-to-many relationship between records of the
same type, where PART is the owner of both PART_USES and PART_USED_ON
set types and COMPONENT is the junction record.
PART_USES is a bill of materials set type that links a PART owner record
through its COMPONENT member records to the part’s subassemblies. The link
to the subassemblies is from COMPONENT member records up to the PART_
USED_ON set type and back to PART owner records.
Database Programming with HP COBOL 5–17