April 10, 2011

Database Design Essentials

The components that are absolutely necessary for a successful database project. There are 10 essentials:

Understand the database’s purpose:
The first essential is that you discover and understand the database’s purpose before doing anything else. Saying that the database’s purpose is “to store records” isn’t good enough. You need to understand the business reason for this database’s existence before it goes into development, much less production. The business reason needs to map not only to the technical specifications but also to the business purpose and the business processes that this database will be supporting.

Get the right tool:
A good CASE tool can help you quickly create different types of data models—such as functional decompositions, system and context diagrams, business process and data flow diagrams, and entity relationship models—each of which will help you communicate to your colleagues the visual components of the proposed system you’re building.

Gather the requirements for the database.
You need to understand the requirements well enough to be able to create visual representations of data, processes, and systems.

Be conscientious when modeling the data:
You need to perform data modeling at multiple levels. You should create the following three models:

Conceptual data model (CDM). The CDM contains the semantics of the information domain that you’re modeling. The CDM defines the scope of the database. Entity classes—the distinct data sets I mentioned earlier—represent things of interest to the organization, and the relationships between the entity pairs assert business rules and regulations. The CDM expresses both the as-is and to-be states and is often created during the Discovery stage.
Logical data model (LDM). The LDM describes the structure of the information domain. It includes criteria such as attribute set details, data types, key status, and individual attribute nullability.
Physical data model (PDM).The PDM defines how the data will be physically stored. You need to map the LDM to a specific database management system (DBMS) platform.

Enforce relationships.
The whole idea of a relational database is to identify and enforce relationships between entity pairs so that data integrity, as defined in the business rules and regulations and represented in the data models, is maintained.

Use the appropriate data types.
Defining appropriate data types and lengths, nullability, defaults, and check constraints when creating tables
Using user-defined types, user-defined functions, and stored procedures that evaluate data when it’s being entered or used
Using Declarative Referential Integrity (DRI) or triggers to enforce relationships between pairs of tables
Using lookup tables to restrict data values when they’re inputted or edited

Include indexes when modeling.:
From the gathered requirements, you should be able to determine which columns will be used for filtering (i.e., in the WHERE clause),sort ( ORDER BY clause)


Standardize the naming convention.

Store the code that touches the data in Server.
The best way to avoid inconsistent rule application and SQL injection is to store code that touches a database’s data as a stored procedure or CLR object.
Document the work.

1 comment:

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