RDBMS

   . A basic Database Management System DBMS) store data in the form of files like records of Strings.
   . DBMS is a collection of programs used to store and read data.
   . RDBMS stands for Relational Database Management System.
   . RDBMS is improved version of DBMS using relational model and it is efficient.

   . Most of the Database Management Systems like Oracle, My-SQL, MS SQL Server etc are RDBMS.

   . Uses table to store data.

   . Table contains rows and columns which stores data in the form of rows and columns.

   . Field is a small entity where data is inserted.

   . Row of a table is called a record which contains specific information of each entity.

   . Column is a vertical entity which contains similar category of information in the table.

      DBMS Vs RDBMS:

         . Key difference between DBMS and RDBMS is that data is stored in the form of files in DBMS and in the form of tables in RDBMS.
         . There is no relation between the data in DBMS like RDBMS.
         . Lot of duplicate data is present in DBMS which is concerning issue.
         . RDBMS use the feature of constraints which reduces redundancy of data.

DBMS	RDBMS
Data is stored in the form of files	Data is stored in the form of tables
Stored in hierarchical or navigation form	Stored in a structured format using constraints
Data redundancy cannot be avoided using Normalization	Supports Normalization which can avoid data redundancy
No security constraints	Data is secured using Integrity Constraints concept
Data cannot be distributed among multiple computers	Data can be distributed among multiple computers
There is no relation between data	Relation exists among the tables
Allows only a single user	Allows multiple users
Suitable to handle small amount of data	Suitable to handle large amounts of data
Examples: Microsoft Access, XML etc	Examples: Oracle, MS SQL server, My SQL etc

    What is SQL?

         . Stands for Structured Query Language.

         . Used to perform operations on database like creating, updating, deleting tables or records.

         . It is just a language which helps us to use database using commands.

         . We need to install any of the databases like Oracle or My-SQL to use SQL.

     Types of Commands in SQL:

             . Data Definition Language(DDL): Used to create, modify and drop structure of database objects. 
               Commands: CREATE, ALTER, DROP, TRUNCATE

             . Data Manipulation Language(DML): Used to store, modify data from databases. 
               Commands: INSERT, UPDATE, DELETE

             . Data Query Languae(DQL): Used to retrieve data from the databases.
               Only one command- SELECT

             . Transaction Control Language(TCL): Used to handle changes that effect databases like commiting, setting a point and rollback to previous change.
               Commands: SAVEPOINT, ROLLBACK, COMMIT

             . Data Control Language(DCL): Used to implement security on database objects.
               Commands: GRANT, REVOKE

      What are Constraints?

         . These are used to limit the data that goes into the table.

         . Can be applied at column level or table level.

         

         . NOT NULL Constraint: Ensures that column cannot have a null value.

         . DEFAULT Constraint: Provides a default value when no data is specified.

         . PRIMARY key: Doesn't allow duplicate and null value in the column.

   

         . FORIEGN key: References the the data from the table assigned with primary key.

         . UNIQUE key: Ensures there is no duplicate data but allows null values.

         . CHECK Constraint: Ensures all values in column satisfies a condition.