Most of us are aware about Database and Database Management System. But do you know how the data is organized in a database. What is the relation between data in database ?
For designing a database structure , which is easy to use and maintains the data security, we need Data Modeling. So we will discuss now about what is data modelling and types of data model as well.
What is Data Modeling ?
In very simple words, Data Modeling is the technique to design data models.Data modeling is the act of exploring data-oriented structures.
Data model is a diagram or flowchart that illustrates the relationships between data. A data model is a conceptual representation of data structures (tables ) required for database and is very powerful in expressing and communicating the business requirements.
There are two ways to create data model – Top down approach and bottom down approach. In Top down approach, data models are created by understanding and analyzing the business requirements. In bottom up approach, data models are created from already existing databases.
Data model is a blueprint or map of database. Although capturing all the relationship in a data model can be very difficult. But well documented data model is very for technical and functional team to create database.
Levels of Data Model :
Basically there are three levels of data modeling –
- Conceptual Data Model
- Logical Data Model
- Physical Data Model
1. Conceptual Data Model –
Conceptual Data Model includes all major entities and highest level relationship between the different entities.Conceptual data model not necessarily includes keys, attributes of tables.Conceptual data model is the stepping stone to design logical data model.
2. Logical Data Model –
This is the actual extension of conceptual data model.A logical data model describes the data in as much detail as possible, without regard to how they will be physical implemented in the database.
Logical Model have following things to make it detailed and self explanatory –
- Includes all entities and relationships among them.
- All attributes for each entity are specified.
- The primary key for each entity is specified.
- Foreign keys (keys identifying the relationship between different entities) are specified.
- Normalization occurs at this level.
3. Physical Data Model –
Physical Data Model is the actual model which will be created in the database to store the data. Physical data model represents how the model will be built in the database. It is the most detailed data model. It includes :
- Tables names
- All column names of the table along with data type and size
- Primary keys, Foreign Keys of a table