week 4

Database management system (DBMS)

• an integrated collection of stored data that is centrally managed and controlled

• a system software component that manages and controls one or more databases

• database component that contains descriptive information about the data stored in the physical data store (sometimes called metadata)

• the standard query language to access and update data in a relational DBMS

Characteristics of a DBMS

• Simultaneous access by many users and many applications

• Direct access to data with a data interface

• Uniform and consistent access

• Integration and distribution of data across multiple servers

• Single desktop – single copy of database

... database is multiple servers within a single data farm

... key is the key chosen by a database designer to represent relationships among rows in different tables

Add primary key attribute of the “one” class to the “many” class as a foreign key

• one to one

• one to many

• many to many

referential integrity is a constraint, stored in the schema, that the DBMS uses to automatically enforce referential integrity

• True

• False

... is a formal technique for evaluating and improving the quality of a relational database schema

A table is in Third Normal Form if it is in 2NF and NO non-key attribute (or set) is functionally dependent on any other non-key attribute (or set)

• True

• False

... database is stored at many locations but not requiring interconnectivity or synchronization

technique to apply exclusive control to a portion of the database to one user at a time

• transaction

• database lock

• shared or read lock

• exclusive or write lock