Lecture 2-DATABASE MODELS lecture 2.pptx
- 2. A database model shows the logical structure of a database, including the relationships and constraints that determine how data can be stored and accessed. Individual database models are designed based on the rules and concepts of whichever broader data model the designers adopt. Most data models can be represented by an accompanying database diagram.
- 3. Types of Database Models 1. Hierarchical database model 2. Relational model 3. Network model 4. Object-oriented database model 5. Entity-relationship model 6. Document model 7. Entity-attribute-value model 8. Star schema 9. The object-relational model, which combines the two that make up its name
- 4. Relational Model • The most common model, the relational model sorts data into tables, also known as relations, each of which consists of columns and rows. Each column lists an attribute of the entity in question, such as price, zip code, or birth date. Together, the attributes in a relation are called a domain. A particular attribute or combination of attributes is chosen as a primary key that can be referred to in other tables, when it’s called a foreign key.
- 6. Hierarchical Model The hierarchical model organizes data into a tree-like structure, where each record has a single parent or root. Sibling records are sorted in a particular order. That order is used as the physical order for storing the database. This model is good for describing many real-world relationships.
- 8. Network Model The network model builds on the hierarchical model by allowing many-to-many relationships between linked records, implying multiple parent records. Based on mathematical set theory, the model is constructed with sets of related records. Each set consists of one owner or parent record and one or more member or child records. A record can be a member or child in multiple sets, allowing this model to convey complex relationships.
- 10. Object Oriented Model This model defines a database as a collection of objects, or reusable software elements, with associated features and methods. There are several kinds of object-oriented databases:
- 12. A multimedia database incorporates media, such as images, that could not be stored in a relational database. A hypertext database allows any object to link to any other object. It’s useful for organizing lots of disparate data, but it’s not ideal for numerical analysis. The object-oriented database model is the best known post- relational database model, since it incorporates tables, but isn’t limited to tables. Such models are also known as hybrid database models.
- 13. Object Relational Model This hybrid database model combines the simplicity of the relational model with some of the advanced functionality of the object-oriented database model. In essence, it allows designers to incorporate objects into the familiar table structure.
- 15. Languages and call interfaces include SQL3, vendor languages, ODBC, JDBC, and proprietary call interfaces that are extensions of the languages and interfaces used by the relational model.
- 16. Inverted File Model A database built with the inverted file structure is designed to facilitate fast full text searches. In this model, data content is indexed as a series of keys in a lookup table, with the values pointing to the location of the associated files. This structure can provide nearly instantaneous reporting in big data and analytics, for instance.
- 18. This model has been used by the ADABAS database management system of Software AG since 1970, and it is still supported today.
- 19. Flat Model •The flat model is the earliest, simplest data model. It simply lists all the data in a single table, consisting of columns and rows. In order to access or manipulate the data, the computer has to read the entire flat file into memory, which makes this model inefficient for all but the smallest data sets.
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