Basic of Data Arrangement &Access
Data hierarchy : Database contains files,file contains records, record contain fields, field contains charracters.
Field (field size, field name, data type): a logical grouping of characters into a word, a small group of words, or a complete number.
Record : a logical grouping of related fields.
File : a logical grouping of related records.
Database : a logical grouping of related files.
Data Management Terminology
Entity : a person, a place, thing, or event about which information is maintained. (Records) describe entities.
Attribute : each characteristic or quality describing a particular entity.(Fields) describe attribute.
Primary Key : field that uniquely identifies the record.
Secondary Key : field doesn’t identify the records uniquely, but can be used to form logical groups of records.
Locating Data in Database
Distributed : complete copies of a database, or porpotions of a database, are in more than one location, close to the user.
Type 1(Replicated Database) :
Type 2(Partitioned Database) :
Database Management System
A set of software programs that provide access to database.
DBMS components :
Data model : defines the way data are conceptually structured.
Data definition language : used to define the content and structure of the database, user define their logical view(schema) of the database using the DDL, relationship, primary key, and secure can be established.
Data Manipulation Language : used to query the contents of the database, store or update information in the database, and develop database applications.
Data Dictionary : stores definitions of data elements and data characteristics.
DBMS benefits :