What are the limitations of file-based systems?
- Separation and isolation of data- Since each program is responsible for its own data a user may ne unaware of potentially useful information in other programs
- Duplication of data when the same data is held by different programs. This may lead to wastage of space and or potentially different formats or values for the same item
- Program-data dependence- This is disadvantageous since if any changes are to be made on the data the application has to be rewritten
- Incompatible file formats- Programs are written in different languages so they cannot easily access each others files
- Inflexibility in querying stored data
- Increase in number of various application programs- Any new requirement requires a new program
What is a database?
a shared collection of logically related data and its description designed to meet an organizations information needs
What is an entity?
A distinct object (person, thing, event, place etc) in an organization that is represented in a database
What is an attribute
A property that describes a certain aspect of an object that we wish to record
What is a relationship?
An association between entities
What is a DBMS?
Software that enables users to create, define, maintain and control access to a database.
It interacts with both the actual database and the application software
What functionalities does a DBMS provide?
- Allows users to specify the types of data as well as the constraints on the data. Done using a data definition language(DDL)
- Allows users to create, read, update and delete (CRUD) data from the database. Done using a data manipulation language (DML)
- Provides controlled access to the data in the database (authorization) . Done using the data control language (DCL)
What is a query language?
Query language (QL) refers to any computer programming language that requests and retrieves data from database and information systems
Give examples of query languages.
Structured Query Language (SQL) Transact SQL (T-SQL) Contextual Query Language (CQL) Object Query Language (OQL) Language Integrated Inquiry (LINQ) Yahoo Query Language (YQL) Bing Query Language (BCL) XQuery
Give examples of DBMSs
MySQL Oracle MS Access SQL Server File Maker FoxPro
What is the function of database application programs?
- Used to create and maintain the database
- Enables the user to access the database
- Access the database, process the data and generate the required information
Give examples of database application programs.
Amazon
CNN.
eBay.
Facebook.
What are the characteristics of the database approach?
- Single repository of data that is sharable by multiple users thus favoring concurrency
- Multiple views ( a subset of a database tailored for the needs of the user) of data that allows some level of customization for the user
- Self describing- System catalogue contains Metadata (data that describes other data) eg definitions of database objects (eg tables) and security information about the type of access users have
- Program-data independence- capability of leaving data intact and accessible regardless of modifications to the database that contains the data.
What are the 5 major components that make a DBMS environment?
- Hardware- Can range from a PC to Network devices
- Software-Collection of programs used by computers in the database system eg DBMS, Operating System and Network software
- Procedures- Instructions and rules that should be applied when designing and using databases
- People-Users of the database
- Data- acts as the bridge between the human (people and procedures) and machine (hardware and software) component
What are the types of roles within a database environment?
- Database Administrator- Management of data within the database. Tasks include maintaining the data dictionary, monitoring performance, and enforcing organizational standards and security.
- Database Designers- Responsible for defining the detailed database design, including tables, indexes, views, constraints, triggers and other database-specific constructs. Solves a problem and makes an entity relationship diagram (ERD).
- Application developers
- End-Users
Describe 5 functions of a DBMS
- Data storage, manipulation and update- The database must allow the user to ~
- A DBMS should provide a user-accessible catalogue that contains descriptions of data items stored in the database
- A DBMS should provide transaction support such that all or none of the updates corresponding to a particular transaction are made
- A DBMS should have concurrency control services to ensure the database is updated correctly when multiple users are updating it at the same time
- A DBMS should provide recovery services in case the database is damaged in any way
- A DBMS should provide authorization services such that only authorized persons are allowed access to the database
- A DBMS should provide support for data communication with hardware
- A DBMS should provide integrity services such that all the data and changes to the data follow pre-specified rules
- A DBMS should provide services to promote data independence from the actual structure of the database
What are the disadvantages of database systems?
- Increased costs- they require sophisticated hardware, software and skilled personnel
- Management Complexity- Introduces changes to an organization that need to be properly managed to ensure they help advance the company’s objective eg new security issues must be handled
- Maintaining currency- Frequent updates are required and application for the latest patches and personnel training
- If the database is not properly backed-up and it fails all data is lost since the storage is centralized
What are the advantages of database systems
- Improved data sharing - End users have access to more and better managed data
- Improved data security- A framework is provided for better enforcement of data privacy and security policies
- Better data integration- Wider access to well-managed data promotes an integrated view of the organizations operations and gives a clearer vision of the big picture
- Minimized data inconsistency- Data inconsistency is greatly reduced (Eg having different record s for Will Brown and William Brown yet they are the same person)
- Improved data access- makes i possible to produce quick answers to ad hoc questions
- Improved decision making- It’s possible to generate better quality information hence better decisions
Discuss five factors you will consider when selecting a Database Management
1) Usability
Consider how user-friendly the system will be for all those members of staff required to use it.
2) Security
Security of your data is an essential aspect of any database implementation.
3) Scalability
Ensure that the system has the capacity to grow with your data and your business.
4) Efficiency
When we talk about the efficiency of DBMS, we usually mean the response time.
5) Implementation and Service Costs
The modifiability and availability of support and documentation needs to be taken into consideration as part of the implementation and Total Cost of Ownership
Give three applications of databases
- In businesses to keep track of customer, staff, accounting information etc
- Keeping track of personal fitness eg using sport watches
- In education to keep track of student information
Describe five properties of a relation in relational databases
Values are atomic.
All of the values in a column have the same data type.
Each row is unique.
The sequence of columns is insignificant.
The sequence of rows is insignificant.
Each column has a unique name.
Integrity constraints maintain data consistency across multiple tables
-
INTRODUCTION TO DATABASES21
-
INTRODUCTION TO DATABASES- ANSI-SPARC16
-
INTRODUCTION TO THE RELATIONAL MODEL22
-
DATA NORMALIZATION19
-
RELATIONAL ALGEBRA14
-
DATABASE DESIGN AND ANALYSIS14
-
ERD MODELLING6
-
ASSORTED2
-
TRANSACTIONS16
-
CONCURRENCY AND SCHEDULING19
-
LOCKING AND TIME STAMPS21
-
SECURITY20
-
SECURITY II6
-
SQL35
