In network model of database , all data is related to each other through a link. By a link we mean that it is an association between precisely two records/data . In hierarchical model records are organized as trees rather than arbitrary graphs.
The hierarchical data model organizes data in a tree-like structure with a single parent for each child record. On the other hand, the network data model allows for multiple parent-child relationships, creating a more flexible and complex network of interconnected records. In the hierarchical model, relationships are one-to-many, while in the network model, relationships can be many-to-many.
two main early navigational data models were the hierarchical model and the CODASYL model (network model)
The hierarchical model is a restricted type of network model. Again, data is represented as collections of records and relationships are represented by sets. However, the hierarchical model allows a node to have only one parent. A hierarchical model can be represented as a tree graph, with records appearing as nodes (also called segments) and sets as edges.
The Hierarchical model organizes data in a tree-like structure with parent-child relationships, allowing each child to have only one parent, which creates a clear, but rigid, hierarchy. In contrast, the Network model allows for more complex relationships by enabling each record to have multiple parent and child records, facilitating a more flexible and interconnected data structure. This flexibility in the Network model can accommodate many-to-many relationships, whereas the Hierarchical model is limited to one-to-many relationships. Consequently, while the Hierarchical model can be simpler to navigate, the Network model offers greater versatility in representing complex data relationships.
Hierarchical data model :Advantages- simplicity- data security- data integrity- efficiency- ease to add and delete recordDisadvantages- implement complexity- database management problem- lack of structural independence- programming complexity- implementation limitation- procedural access languageNetwork data model :Advantages- easy to access data- can handle more relationship types- data independence- data integrity- data independenceDisadvantages- system complexity- lack of structural independence- procedural access language
The relational model is a model in which data is isolated by object and foreign keys to those objects which is organized in tables with multiple columns or attributes. The hierarchical model is a model in which the data is organized in a tree structure that allows repeating information using parent/child relationships.
Relational model of database is a good way to represent the database. Also network data model and hierarchical model can be used depending on the requirements.
Hierarchical databases organize data in a tree-like structure with parent-child relationships and a strict one-to-many hierarchy, while network databases use a more flexible model with many-to-many relationships through pointers or links between records. Hierarchical databases are faster for accessing data along predefined paths, while network databases allow for more complex data relationships but can be more complex to manage.
The four primary database models are the relational model, hierarchical model, network model, and object-oriented model. The relational model organizes data into tables with rows and columns, allowing for easy querying through SQL. The hierarchical model structures data in a tree-like format, where each record has a single parent. The network model allows for more complex relationships through a graph structure, while the object-oriented model integrates database capabilities with object-oriented programming principles.
-> A record based data model is used to specify the overall logical structure of the database.-> In this model the database consists of a no. of fixed formats of different types.-> Each record type defines a fixed no. of fields having a fixed length.-> There are 3 principle types of record based data model. They are :1. Hierarchical data model.2. Network data model.3. Relational data model.
The network model is a database model conceived as a flexible way of representing objects and their relationships. Its original inventor was Charles Bachman, and it was developed into a standard specification published in 1969 by the CODASYL Consortium. Where the hierarchical model structures data as a tree of records, with each record having one parent record and many children, the network model allows each record to have multiple parent and child records, forming a lattice structure. The chief argument in favour of the network model, in comparison to the hierarchic model, was that it allowed a more natural modeling of relationships between entities. Although the model was widely implemented and used, it failed to become dominant for two main reasons. Firstly, IBM chose to stick to the hierarchical model with semi-network extensions in their established products such as IMS and DL/I. Secondly, it was eventually displaced by the relational model, which offered a higher-level, more declarative interface. Until the early 1980s the performance benefits of the low-level navigational interfaces offered by hierarchical and network databases were persuasive for many large-scale applications, but as hardware became faster, the extra productivity and flexibility of the relational model led to the gradual obsolescence of the network model in corporate enterprise usage.
Navigation in the Relational Data Model is simpler than in the Hierarchical Data Model due to the relational structure of tables linked by common keys. In the Relational Data Model, data is organized into tables with rows and columns, allowing for easy querying and retrieval of information using SQL queries. On the other hand, in the Hierarchical Data Model, data is organized in a tree-like structure with parent-child relationships, making navigation more complex and requiring traversal of multiple levels to access specific data points.