DBMS– Stands database management system
What is data
Data is any known fact or any smallest information that can be recorded and have implicit meaning
e.g: Prince, computer science, information technology
What is Database
It is a collection of related data. Here related data means if are collecting the information of employee it should be related collection of the employee data
What is a Database system?
The database system is a system in which a user uses the database technology in order to achieve an organized, store a large number of dynamic associated data with the help of hardware, software and operating system.
Database system composed of five major parts
1. Hardware
2. People
3. Data
4. Software(DBMS)
5. Procedure
DBMS
It is a set of software program that allows users to create edit and update data in database files and store and retrieve data from those database files.
example- MSSQL SERVER, MY SQL, SQL, ORACLE
Property of DBMS
Completeness
This property ensures that users can access the data they want including Adhoc queries.
Integrity
Integrity database integrity ensures that data inter into the database is accurate and consistent.
Data accuracy refers to that data value must be the right value and must be represented in a consistent manner
Consistency
Consistency of data refers that if a person changes his phone number so it should be changed everywhere in database where is telephone data is saved.
Flexibility
It is the ability to upgrade or change the functionality of the database.
Efficiency
Efficiency ensures that should not wait for a long time
Usability
Usability ensure that data can be accessed and manipulated in ways that match the user’s requirement
View of Data
It refers that how data is actually stored in the database, what data and structure of data is used by the database for data.
Data abstraction
Data abstraction means hiding the details from users about how the actual data is a stored or accessed in the database.
So when a user comes and wants to access any data, he won’t be able to access the data if he has gone through this data structure. To simplify the interaction of user and database, DBMS hides some information that is not of user interest this is called Data abstraction.
Database schema
The overall design and description of the database is in general called the database schema.
Physical schema
It is the lowest level of data abstraction and described in detail how the raw data is actually stored using a complex low-level data structure.
Logical schema
It is used by database administrators to describe the data stored in the database and the relationship between those data.
View schema
This is the highest level of data abstraction and deals with the way a given application program view the data in the database.
Database instance
It is the collection of information stored at any particular time in the database.
Data independence
It is the ability to modify the structure of a database in one level without affecting the database structure in a higher level.
Physical data independence
It is the ability to change the internal or storage schema of a database without having to change the logical schema.
Logical data independence
It is the ability to change the logical or conceptual schema of a database without having to change the view scheme of the database.
Data model
These are collection of conceptual tools for describing the data, the relationship between the data,the rules applicable on the data etc.
Hierarchical Model
It is the oldest of database models where records are logically organized in a parent-child relationship to form a hierarchy.
Advantages of the hierarchical model
The model allows easy addition and deletion of information.
Data at the top of the hierarchy is very fast to access.
It is good for entities that have one to many relationships between them.
Disadvantages of the hierarchical model
It requires data to be repetitively stored in many different entities
The database can be very slow when searching for information on the lower entities, as it requires the DBMS to run through the entire model from top to bottom till the data is found
Many to many relationships are not supported and can have only one to many relationships
Relational model
In this data model, the data is represented as a collection of tables. The tables are joined by relationships using various keys.
Advantages of the relational model
The representation of the information in the form of tables consisting of rows and columns is much easier to understand.
The different tables can be easily combined and manipulated to extract the required information
The use of relational algebra and relational calculus to manipulate the relational relation between tables removes any ambiguity which usually may arise in the network model.
Disadvantages of the relational model
If the number of table is larger than creating the database may take some time to join our son to combine data from different table may require large data storage capacity
Network model
It is similar to the hierarchical model parent-child relationship but allows a record to be a child of more than one parent records.
Advantages of the network model
The model retains almost all the advantages of the hierarchical model but the data access is easier than the hierarchical model
The network model is conceptually simple
The model support both one-t-many and many-to-many relationships
Disadvantages of the network model
The model is difficult to implement and maintain
The whole database structure is a complex one as it involves a lot of pointers/links
Making structural changes to the database is difficult in most cases
ER model(Entity-relationship model)
It is an object-based data model whose basic component is the ER diagram, which represents a blueprint for database design.
Entity
It is an object having a physical or conceptual existence and that can be easily identified in the real world
Attribute
It is a property of the given entity that helps to describe an entity
Relationship
It indicates the association between different entities i.e; it determines how are given entity is related to another entity
Data definition language(DDL)
It is a database language used to specify the design and structure of a database.
creating a database comprises of creating the internal, conceptual, and view schema. In DBMS where a strict separation between these three levels is not maintained a single language called data definition language is used to create the internal and conceptual schema.
Data manipulation language(DML)
It is a database language used to access and manipulate the data in a database.
Data control language(DCL)
It is a database language used to define activities that are not part of DDL or DML like providing access privileges to users.
Procedural DML
To retrieve particular information in such a language, the user has to specify both the specific data required along with how to get that data.
Components of DBMS
Storage manager
This module of DBMS software is used to modify information in the database and retrieve information from the database when requested by the higher level
Transaction manager
This module of storage manager maintain the execution of different transaction simultaneously without any conflict and helps in recovering lost data in case of a failed transaction.
Query Processor
This module of the DBMS software converts a query as submitted by the user and express in higher-level languages, into a sequence of commands in a low-level language
Database administrator (DBA)
DBA is a technical person who is responsible for the overall control and fine-tuning of the database and granting different access to a database user.
