Data Abstraction, Users, Data Models and Languages
In this tutorial we will discuss about the concepts of data abstraction, users of the database, database models and introduction to data languages.
Data Abstraction
Data abstraction shows how the data is stored from the low-level to the high-level. In this data abstraction three levels are there:
Physical Level:
This level shows how the data is stored in the database from the low to complex level data structures.
Logical Level:
This level describes what sort of data is stored and the relationship among the data that is present in the database as simple structures.
View Level:
It is the highest level of the data abstraction visible to the user. It is only a specific part out of the entire data visible to the user that can be accessible by the
user.
Instances and Schemas
Instance:
The time interval in which the content present in the database is known as the instance of the database
Schema:
The logical description of the database that stores the data is known as the schema. Physical schema and logical schema are the two types that describe the physical and logical levels in Data Abstraction respectively.
Database Users
Naive Users:
The users interacting the database using the application program are known as the naive users
Application Programmers:
They are interacting the database by writing the programs to interact with the database
Sophisticated Users:
They can directly interact with the database and can change the database accordingly.
Specialized Users:
These users will use the database for the sake of a particular purpose or application.
Data Models
It defines the structure and is a tool to describe the data, relationships with the constraints of the database as discussed in Data Abstraction
The most used data models are:
Relational Model:
In this model, the data and the relationship among the data are stored in the tables.
Entity-Relationship Model:
The entity will have permanent existence in the database with particular attributes and can be identified uniquely. The relationships between the entities will be present in this model.
Database Languages
There are 4 different database languages with the following set of commands associated with each language.
- Data Manipulation Language(DML) – Data Abstraction:
- Select
- Insert
- Update
- Delete
- Merge
- Data Definition Language(DDL) – Data Abstraction:
- Create
- Alter
- Drop
- Truncate
- Comment
- Rename
- Data Control Language(DCL) – Data Abstraction:
- Revoke
- Grant
- Transaction Control Language(TCL) – Data Abstraction:
- Commit
- Savepoint
- Rollback
- Set
- Transactions
For more information visit the section of SQL.