These are some notes for the Database Management System. In these notes you will found many topics. These notes focuses on the fundamentals of the databases and the Management Systems available for making database freindly. This pdf contains some topics like
1. what is database and its purpose -
A database is a collection of many interreleted data. In database all the data is organized in a structured way so that anyone can efficiently use it and can easily upadate, read, create and delete the data. there are many purpose for which we need a database like-
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Data Organization: Databases structure data into tables, rows, and columns, making it easier to organize, manage, and search for specific information.
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Data Backup and Recovery: Databases often include features to back up data and recover it in case of accidental loss or system failures.
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Data Security: Access to the data can be controlled and restricted, ensuring that only authorized users can view or modify sensitive information.
2. Characteristics, Advantage and disadvantage of DBMS -
A Database Management System (DBMS) is software that allows users to define, create, manage, and manipulate databases. It provides an interface between the database and its users or application programs. Below are the key characteristics, advantages, and disadvantages of a DBMS :
Characteristics of DBMS
- Data Abstraction: DBMS hides the complexities of data storage, allowing users to interact with high-level data representations.
It provides different levels of data abstraction: physical, logical, and view levels.
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Data Independence: Data can be changed without affecting the application. This refers to logical and physical data independence.
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Data Security and Integrity: DBMS provides features to enforce security and data integrity, ensuring only authorized users can access or modify the data.
Advantages of DBMS
- Data Consistency.
- Improved Data Sharing.
- Data Security.
- Backup and Recovery.
Disadvantages of DBMS
- Cost.
- Complexity.
- Performance.
- Risk of System Failure.
3. Actors on the scene -
These are the person that work on the DBMS there are various actors some of them are :
1. Database Administrator (DBA)
- The DBA is responsible for the overall management and control of the database system. They handle the design, configuration, performance tuning, security, and backups of the database.
2. Database Designers
- Database designers are responsible for the structure of the database. They design the schema, tables, relationships, and constraints to meet the needs of the users.
3. End Users
- End users are individuals or applications that interact with the database. They can query, update, and retrieve data, depending on their access level.
4. Workers Behind the scene
These are the persons that work on the database but thay are not showed anywhare they work silently. In other words "workers behind the scene" refers to the internal components and background processes that operate within the system to manage and manipulate data efficiently, ensuring that users and applications can interact with the database seamlessly. Some of them are :
- Query Processor
- Storage Manager
- Transaction Manager
- Operators and Maintanence personnel
5. Database Models -
database models are of four types :
1. Hierarchical Model :
This model organizes data in a tree-like structure where each record has a single parent, but it can have multiple children. It's best for scenarios where data has a clear hierarchy, such as organizational structures.
2. Network Model :
This model expands on the hierarchical model by allowing more complex relationships. A record can have multiple parent and child records, forming a graph structure. This allows many-to-many relationships.
3. Relational Model :
The most popular and widely used model, the relational model organizes data into tables (relations) where each row represents a record, and each column represents a field. Relationships between tables are established through keys.
4. Object-Oriented Model :
This model integrates database concepts with object-oriented programming. Data is represented in the form of objects, similar to how it’s structured in object-oriented programming languages like Java or C++.
6. DBMS Architecture levels -
NOTE: The characteristics that allow the data-program and data-operation independence is called Data Abstraction.
1. Internal Level
- What It Is: This is the lowest level of data abstraction. It deals with how the data is physically stored in the database.
2. Conceptual Level
- What It Is: This is the middle level of abstraction. It describes what data is stored in the database and the relationships between that data.
3. External Level
- What It Is: This is the highest level of abstraction. It defines how individual users view the data.
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