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A Database is
an information model because it uses information to model something from the real world
Logical Database Components are
Entities and Atrributes
Entites
Anyone or anything we keep information on, instances
Attributes
describes and identifies entities; aka characteristics, measures, and dimensions
Physical Database Components
Servers and Data
Servers
powerful computers
Data
kept on computers
Centralized
in a single place, easier to maintain
Distributed
multiple locations, separate storage and processing, and makes users experience easier
Server Architecture
Data
Client Architecture
Application Software
A.C.I.D acronym defines
the reliability of a database
Atomicity in A.C.I.D
Transactions are all or nothing. Either the entire transaction occurs—or nothing occurs.
Consistency in A.C.I.D
Only valid data is saved
Isolation in A.C.I.D
transactions do not affect each other
Durability in A.C.I.D
written data will not be lost, transactions are permanent
Database Administrator (DBA) is
responsible for everything in a database. Ensure that a database is available as needed and is protected and secured from unauthorized users and activities
Database Management System (DBMS) Structure Diagram
a program through which users interact with the data stored in a database
Metadata is
Information about information
Schema is a
model or blueprint of the tables and relationships between the tables. Overarching organization of databases
A Relational Database is
a structure that contains data about many categories of information displayed in two-dimensional tables (relations)
Relational Data Model is made up of
Columns (fields) and Rows (records and tuples)
Columns in a table (relation) are often called
fields or attributes
Rows in a table (relation) are often called
records or tuples
Records are
a group of related fields (rows)
Table (aka File and Relation) is
a group of records
A database consists
of a group of tables
The entries in the table are Single-Valued meaning
each intersection of the row and column in the table contains only one value
Primary Key is
the column or columns that uniquely identify a single record
QBE (Query-By-Example) is
a visual GUI (graphical user interface) approach to writing queries.
Note
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