Intoduction to database systems Flashcards
What was the first way of storing data
Manual File systems
What was the initial approach to computerizing databases
File-based systems
How do file-based systems work?
What are some of the disadvantages of manual filing systems
- Decentralization
2. Delay in decision making
What are some of the disadvantages of the file-based system?
- Possible replication of data
- Atomicity
- Program data dependency (to update the data you have to rewrite the program)
- Data security and recovery (What happens if the system crashes you are unable to recover the data)
- There is a limited number of queries.
What is a database?
Is a collection of logically related data
What is a database?
Is a collection of logically related data.
What is a feature of databases?
- It is a shared collection.
* User classification.
Why was the database system introduced
To bridge the gaps of the file-based systems.
What is an entity?
A distinct object in the organization that is to be represented in the database. e.g a person
represented by nouns
What is an attribute?
A property that describes some aspect of the object that we wish to record.
What is a relationship?
This is an association between entities.
We ask how do the entities interact?
represented by verbs
What is a database management system?
Application software that enables you to define, create maintain and control access to the database.
What are the functional groups of DBMS
1. Allows users to specify the types of data as well as the constraints on the data to be stored in the database. Uses DDL (Data Definition Language) 2. Allows users to read, create, update and delete data from the database. Uses DML (Data Manipulation Language) 3. It provides controlled access to the data stored in a database. Uses DCL (Data controlled language )
Characteristics of the database approach
- Single repository of data
- Multiple views of data ( to support individual needs of users)
- Self-describing
- Program data independence
