Database Reference
In-Depth Information
6
Transforming Data Models
into Database Designs
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To understand how to transform data models into
database designs
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To be able to identify primary keys and understand when
to use a surrogate key
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To understand the use of referential integrity constraints
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To understand the use of referential integrity actions
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To be able to represent ID-dependent, 1:1, 1:N, and N:M
relationships as tables
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To be able to represent weak entities as tables
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To be able to represent supertype/subtypes as tables
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To be able to represent recursive relationships as tables
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To be able to represent ternary relationships as tables
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To be able to implement referential integrity actions
required by minimum cardinalities
This chapter explains
the transformation
of entity-relationship data models into relational
database designs. This transformation consists of
three primary tasks: (1) replacing entities and attributes with
tables and columns; (2) representing relationships and maximum cardi-
nalities by placing foreign keys; and (3) representing minimum cardinality by
defining actions to constrain activities on values of primary and foreign keys.
Steps 1 and 2 are relatively easy to understand and accomplish; step 3
may be easy or difficult, depending on the minimum cardinality type. In this
chapter, we will create database designs, and we will implement a database
design in Chapter 7 when we build a database using SQL DDL and DML.
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