Why SQL is Important ?

• Can Create DATABASE and TABLES from SQL.

• Can Insert the records in database from SQL.

• Can Delete records from the database by SQL.

• Can Update the records in database from SQL.

• Can Retrieve the data from database from SQL.

• Note-: Before knowing the SQL Database, you must take the Database information .

SQL Database

• SQL Stands for Structured Query Language.

• SQL is provides best user interface and very simple database programming language.

• SQL is 4th generation database programming language.

• SQL is a language that operates the database management system.

• SQL is designed for database mgmt. system in RDBMS (Relational database mgmt. system).

• SQL is the only language that the DBMS understands.

• Exchange of information between Programmers and DBMS with the help of SQL.

• Generally SQL is called S-Q-L.

• SQL is based on relational algebra and tuple relation calculus.

• SQL is used for database creation, deletion, fetching rows or columns and modifying rows and columns.

Database Keys

Super Key:

Definition: A super key for an entity is a set of one or more attributes whose combined value uniquely identifies the entities in the entity set.

e.g. for an entity set Employees, that set of attributes(emp_name, address) can be considered to be a super key, if we assume that there no two employee with the same name emp_name and same address.

Primary key:

Definition: In the relational database management system the primary key is uniquely identifies the each record in the table and must never be the same for two records.

          

e.g. emp_code can be primary key for the entity set Employee.

The primary key should be chosen such that its attribute are never or very rarely changed. For the instance ,the address field of the person should not be the part of primary key, since it is likely to change. emp_code, on the other thand , is guaranteed to never change, till he is in the organization .   

What is DBMS ?

Importent Point's

1. DBMS stands for database management system.
2. The Database is a Collection of Information.
3. The database is organized in such a way that information can easily access, manage and update.
4. In  the database, we can quickly select the desired data.  

So we can say that is a general purpose software system that gives us the following features.

Defining-: Specifies data types, structures and constraints for store data in the db.

Constructing-: The process of storing data in any storage medium is controlled by DBMS.
Manipulating-: In this, the data present in the database is updated, retrieve and reports are generated.

   

THANK YOU!