Monday, 28 December 2015

Conceptual data model

Conceptual data model is a map of key concepts and rules binding these key concepts for a specific business, for a particular audience, that used for databases. Key concepts are both basic and critical to your business. Basic means this term is mentioned many times a day in your organisation in conversation among business people, such as CUSTOMER, EMPLOYEE, PRODUCT, etc.Critical means the business would be very different or non-existent without this key concept. For example, without the concept PRODUCT, your business may become non-existent.

Saturday, 26 December 2015

Thursday, 24 December 2015

Relationships and Cardinality

In real world, entities have relationships with other entities.  Relationships define how two entities are associated with each other. The data modeling captures the nature of relationship between two entities. For example, the entity 'Customer' buys the 'Product' and the entity 'Vendor' sells the 'Product'. It captures the rules between these two entities. If two entities are Person and Telephone Number, the relationship may capture the rule "Each Person may have many Telephone Numbers" and "Each Telephone Number must belongs to one Person." 

Monday, 21 December 2015

Data fields and domains

In previous post we have seen about the entities, in this post let us see about the data fields and domains. Data field is nothing but a column header or label describing instances of an entity. The data field Customer Name describes name of each Customer. The data field Model Number identifies each model.

Friday, 18 December 2015

Thursday, 17 December 2015

Levels of a data model

There are three different levels of Data Model, this makes the model either at a very broad and high level conceptual view, or a more detailed logical or physical view.

The levels of different models are given below,
  1. Conceptual data model (CDM) or Subject area model (SAM).
  2. Logical data model (LDM).
  3. Physical Data Model (PDM).

Wednesday, 16 December 2015