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Defining Requirements and Documenting the Design

Designing the data model and the tables

  • 3 things to know
  • A2 Unit 2

Overview

Deriving the tables from the client's own documents, normalising to third normal form, recording every column with its type, size, validation and key role, and choosing the integrity rule for each relationship.

What you need to know

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Key term

Define a data model in a solution design.

Key term

How are the entities for the data model found from the requirements?

Key term

What does an ER diagram contribute to a design document?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define a data model in a solution design.

    Model answer

    A data model shows the entities the solution stores, the attributes of each and the relationships between them.

  2. 2

    How are the entities for the data model found from the requirements?

    Model answer

    Entities are the things the business must keep information about, and are usually the nouns that recur through the requirements.

  3. 3

    What does an ER diagram contribute to a design document?

    Model answer

    An ER diagram shows every entity and every relationship on one page, so the structure can be checked before any table is built.

  4. 4

    How is a one-to-many relationship carried into the table design?

    Model answer

    The primary key of the table on the one side is placed into the table on the many side as a foreign key.

  5. 5

    How is a many-to-many relationship handled in the table design?

    Model answer

    A link table is created holding the primary key of each of the two tables, turning the relationship into two one-to-many relationships.

  6. 6

    What must the table design record for every field?

    Model answer

    The design records the field name, the data type, the field size, any validation rule and whether the field is a key.

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