- ideal for small amounts of data
- human readable or edited by hand
- good for simple lists
- more costly in time and processing power
- data split up using a common delimiter like comma or TAB
- one line per records
- very prone to corruption
- no inherent locking mechanisms
Relational Database Model
- MySQL, Microsoft SQL Server , Oracle, Access , Portgress SQL
- Tables represent real world objects,
- each field is an attribute of the object
- table - students
- field - firstname. lastname, Class, Age, Village
- record- Nimal, Perera, 12A, 17, Penideniya
- tables can be linked to each other (students --> subjects , subjects > teachers, students ---> marks <----Subjects <---- Teachers
- databases designed efficiently
- no duplication of any data;
- maintain database integrity.
- Can be huge saving in file size,
- deals with large volumes of data.
- have "built in" functions to help retrieve, sort and edit the data
- RDBMS - relational database management system
- developed by E.F. Codd.
- A relational database allows the definition of data structures, storage and retrieval operations and integrity constraints.
- data and relations between them are organised in tables.
- A table is a collection of records and each record in a table contains the same fields.
- based on the Relational Algebra and set theory
Hierarchical Database Model
- Organizes data in a tree structure (parent and child data)
- Data in a series of records, which have a set of field values attached to it.
- have record types. These record types are the equivalent of tables in the relational model,
- individual records is the equivalent of rows.
- To create links between these record types,uses Parent Child Relationships.
- 1:N mapping between record types.
- uses Binary trees, like
- an organization stores information on an employee ( name, employee number, department, salary)
- an store information about an employee's children, (name and date of birth)
- The employee and children data forms a parent, child hierarchy
- If an employee has three children, three child segments associated with one employee segment.
- restricts a child segment to having only one parent segment.
- popular in late 1960s - 1970s. (IBM)
Network Database
- Some data modeled with more than one parent per child.
- permitts modeling of many-to-many relationships in data.
- The data model is a simple network
- The CODASYL network model is based on mathematical set theory.
Object/Relational Databases
- ORDBMSs
- adds new object storage capabilities to the relational systems at the core of modern information systems.
- to integrate management of traditional fielded data with complex objects
- (geospatial data, audio, video, images, and applets)
- tabular structures and data definition languages (DDLs) w
- SQL3, ODBC, JDBC (IBM, Informix, Sun and Oracle )
Object-Oriented Database Model
- adds database functionality to object programming languages.
- useful when we have complex relationships between data
- C++, Smalltalk and Java
- The power of the OODB comes from persistent data in databases, and transient data in executing programs.
- object DBMSs have no performance overhead to store or retrieve interrelated objects.
- mapping of object programming language objects to database objects
- provides higher performance
- better management of the complex interrelationships between objects.
- financial portfolio risk analysis systems
- telecommunications service applications
- world wide web document structures,
- design and manufacturing systems
- hospital patient record systems
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