Logical Data Model

729 Words3 Pages
Data Models: Data models describe how data is connected to each other and how that process and stored inside the system. Hierarchical Model: The hierarchical data model is like trees structurethat present data to users in tree structure. In hierarchical model each record looks like an organizational chart with one top level segment called root. The upper segments are connected logically to the lower segments like as parent and child relationship, and a parent segment can have many children but a child segment can have only one parent. In other words the hierarchical model design is that uses a one to many relationships or links anumber of disparate elements to owner or parent records. Network Model: Network model data allow the network…show more content…
There are several different levels of data modelling such as; • Conceptual data model • Logical data model • Physical data model Conceptual Data Model: Conceptual model is high level model that identifies the higher level relationship between different entities. . Its created by gathering all the business requirements from various sources like business analysts, discussion, documents, management experts and end users that do reporting on the database also its includes all major entities and relationships. Logical Data: Logical data describes the data in as much details as possible and it does include all entities and relationships among them. In logical data all attributes for each entity and the primary key and foreign keys are specified. Physical Data Model: Physical data model about how data will form in the database. . It will specify all the column and tables. This database shows all the structures of tables that include, column of data type, column of names, column of constrains, relationship between tables, primary key and foreign key. The foreign key is use to identify relationship between tables. Feature and…show more content…
Entities are representing by square or round corner. Entity Relation Diagram (ERDs): Entity relationship diagram is a design tool that represent the data system in graphical. ERDs provide a high level theoretical data model and composed of entities, attributes and relationships. A user has to connect a table with other tables to create a relationship between them. Entity attributes and identifiers: Entity attributes are property of an entity that can have any value from domain and they have any number of attributes. Database is used for to store information then user can use it when its need in order to achieve this task user has to identify each entity. Attributes can have different values than any other entity. There are two types of entity attributes; Transient and Persistent. Persistent attribute is persisted and derived from database whereas the value will not be persisted and derived in a transient attribute. Relationship types: there are three types of relationships One –to –one: In one-to-one relationship both side tables will have one record on both sides such as; Husband

More about Logical Data Model

Open Document