Technical data

Figure 5–6 One Occurrence of Set PART_SUPPLY
PART_SUPPLY
S−1 S−7
PART A
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The DBA can specify a set type where each PART record occurrence can own
SUPPLY record occurrences. Figure 5–7 is a Bachman diagram that shows the
relationship between PART record types and SUPPLY record types. Bachman
diagrams give you a picture of the schema or a portion of the schema. Each
record type is enclosed in a box. Each set type is represented by an arrow
pointing from the owner record type to the member record type or types. Thus, in
Figure 5–7, PART is the owner record type of the PART_SUPPLY set type, and
SUPPLY is the member record type.
Figure 5–7 Set Relationship
SUPPLY
PART_SUPPLY
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PART
You can have many set relationships in a subschema. Figure 5–8 shows a set
relationship where vendor records are also owners of supply records. You would
use this relationship when many parts are supplied by one vendor, and many
vendors supply one part. For example, Figure 5–9 shows a gasket supplied by
three vendors. The supply records show the minimum quantity each vendor is
willing to ship.
5–10 Database Programming with HP COBOL