What is SQL?
The Structured Query Language (SQL) is a standard programming language to access and manipulate databases. SQL allows the user to create, retrieve, alter, and transfer information among databases. It is a language designed for managing and accessing data in Relational Data Base Management System (RDBMS).
How to create a Database?
To create a database, type the following command in the prompt:
CREATE DATABASE database_name;
Example:
If you want to create a database containing information about the students then you can type,
CREATE DATABASE student;
NOTE: Any name can be given as database_name. In my example, I have taken it as student.
COMMANDS OF SQL
SQL commands are divided into 5 categories:
DDL – Data Definition Language
DML – Data Manipulation Language
DCL – Data Control Language
TCL -Transaction Control Language
DQL – Data Query Language
SQL commands under DDL are:
| CREATE | To create tables in the database. |
| ALTER | Alters the structure of the database. |
| DROP | Delete tables from database. |
| TRUNCATE | Remove all records from a table, also release the space occupied by those records. |
SQL commands under DML are:
| INSERT | Inserts data into a table. |
| UPDATE | Updates the existing data within a table. |
| DELETE | Delete all records from a table, but not the space occupied by them. |
SQL commands under DCL are:
| GRANT | Grants permission to one or more users to perform specific tasks. |
| REVOKE | Withdraws the access permission given by the GRANT statement. |
SQL commands under TCL are:
| COMMIT | Saves any transaction into the database permanently. |
| ROLL BACK | Restores the database to last COMMIT state. |
| SAVE POINT | Temporarily save a transaction so that you can ROLL BACK. |
SQL commands under DQL are:
| SELECT | It displays the records from the table. |
Now let us see how to create a table using SQL commands.
You can create a table by using the CREATE TABLE command.
Syntax:
CREATE TABLE table_name
( column name <data type> (size),
column name <data type> (size),……
);