After discussing the elementary steps now let's enter into technical complexities of the database system. There are three major cycles of database design, and within each, minor cycles. The major cycles are:
• Conceptual: The conceptual cycle enables a creation of accurate database design that reflects the in-place business policy of the organization.
• Logical: The logical cycle starts with the conceptual design andincorporates the requirements of the specific DMBS through which the DBMS operates.
• Physical: The physical cycle begins with the logical database and folds-in the requirements of the operational environment.
It is important to note that these cycles exist independently and might take different table structures. They must, however all be mapped one to the other.
During the entire database design process the database design from each cycle is maintained in a repository. Each major cycle transformation is expressible through SQL syntax changes. This way the re-transformation can always be accomplished.
Components of Database Design:
Entity: It refers to logical collection of things that are relevant to database. The database table is a physical counterpart of an entity.
Attribute: It refers to descriptive or quantitative characteristic of an entity. The database column or field is a physical counterpart of an attribute.
Primary Key: It refers to an attribute or combination of attributes that identifies each instance of an entity. It should be note that primary key cannot be null and the value assigned to primary key should not change over time.
Relationship: It refers to a logical link between two entities. Most relationships between entities are of the "one-to-many" kinds in which one instance of the parent entity relates to many instances of the child entity.
Then, there is “many to many” relationships . In a "many-to-many" relationship, many instances of one entity relate to many instances of the other entity. "Many-to-many" relationships need to be resolved in order to avoid data redundancy.
Cardinality: It refers to the feature that helps in understanding the nature of relationship between the child entity and the parent entity. There are four kinds of cardinality.
You must keep in mind that every database management system vMay 23, 2006ding utilities, and data update performance reactions. However, it is imperative to design the database system that suits the user's requirements. It should help in the management of conflicts of an enterprise and improve upon productivity.
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