COMPLETING THE LOGICAL DESIGN - Database Design and Development: An Essential Guide for IT Professionals - page 335

CUSTOMER

ORDER

CustNo CustAddr CustName

OrdrNo

OrdrDate OrdrAmt CustNo

.

.

.

.

PAYMENT

CHANNEL

OrdrNo PmntNo

PmntDate PmntAmt

ChnlID

ChnlName

.

.

.

GROWER SHIPMENT

GrwrID GrwrName

OrdrNo ChnlID GrwrID ShipDate ShipQty

.

.

.

PRODUCT FLOWER

ProdID ProdID

ProdCost ProdCost FlwrName FlwrSize

.

.

.

ARRANGEMENT

ProdID ProdCost ArngeType

.

.

Figure 11-8 Representing relationships for florist business.

Rules and Constraints

This step in the logical design includes representation of the following in the
relational data model:

• Reduction of many-to-many relationships into multiple one-to-many relation-
ships
• Representation of foreign keys as additional columns
• Indication of optional and mandatory relationships through minimum cardi-
nality indicators

Once this step is completed, logical design comes to an end, to be followed by
physical design.

DESIGN FOR THE RELATIONAL DATA MODEL

Before going through the completion of the logical design for the relational data
model, let us recapitulate the basic features of the relational model. This refresher
will help you appreciate the special requirements for going through this phase of