A Data model is a conceptual representation of data structures (tables) required for a database and is very powerful in expressing and communicating the business requirements.Data Modeling Overview:
A data model visually represents the nature of data, business rules governing the data, and how it will be organized in the database. Data Models are created for OLTP databases by normalizing the data and for OLAP databases, data models are created by de-normalizing the data. Usually Data Models contains the key database objects like tables, columns, relationships, constraints etc.
Data Modeling Tools:
• Oracle Designer
• SAP Sybase Power Designer
• Rational Rose
• MS Visio
Two phases of data modeling are as follows:
1) Logical modeling
2) Physical modeling
Logical data Modeling:-
•Includes entities (tables), attributes (columns/fields) and relationships (keys).
•Uses business names for entities & attributes
•Is independent of technology (platform, DBMS)
•Is normalized to fourth normal form(4NF)
Physical Data Modeling:-
•Includes tables, columns, keys, data types, validation rules, database triggers, stored
Procedures, domains, and access constraints
•Uses more defined and less generic specific names for tables and columns, such as
Abbreviated column names, limited by the database management system (DBMS)
and any company defined standards
•Includes primary keys and indices for fast data access.