DataBase Management Systems

Selection Operation

Selection Operation Consider the query to find the assets and branch-names of all banks who have depositors living in Port Chester. In relational algebra, this is (customer deposit branch))...

Measures of query cost

Estimation of Query-Processing Cost To choose a strategy based on reliable information, the database system may store statistics for each relation r: – the number of tuples in r....

Query Interpretation

Query Interpretation Why do we need to optimize? A high-level relational query is generally non-procedural in nature. It says “what”, rather than “how” to find it. When a query...

Specialization

Specialization Specialization is a process, which is opposite to generalization, as mentioned above. In specialization, a group of entities is divided into sub-groups based on their characteristics. Take a...

Mapping Constraints

Mapping Constraints An E-R scheme may define certain constraints to which the contents of a database must conform. Mapping Cardinalities: express the number of entities to which another entity...

2- PHASE COMMIT PROTOCOL

Distributed Database A distributed database is a database in which storage devices are not all attached to a common CPU. It may be stored in multiple computers located in...

Database Administrator (DBA)

Database Administrator The database administrator is a person having central control over data and programs accessing that data. Duties of the database administrator include: Scheme definition: the creation of...

Database Users

Database Users The database users fall into several categories: Application programmers are computer professionals interacting with the system through DML calls embedded in a program written in a host...

Three Level Database Architecture

Three Level Database Architecture   Data and Related Structures Data are actually stored as bits, or numbers and strings, but it is difficult to work with data at this...

Introduction to Database Managment System

Database Management Systems A database management system (DBMS), or simply a database system (DBS), consists of A collection of interrelated and persistent data (usually referred to as the database...