Introduction To SQL And SQL Commands

In this article, we will learn about SQL and SQL Commands.

SQL

SQL stands for Structured Query Language. SQL is used to create, remove, alter the database and database objects in a database management system and to store, retrieve, update the data in a database. SQL is a standard language for creating, accessing, manipulating database management system. SQL works for all modern relational database management systems, like SQL Server, Oracle, MySQL, etc.

SQL commands can be categorized into five categories based on their functionality.

DDL

DDL stands for data definition language. DDL commands are used for creating and altering the database and database object in the relational database management system, like CREATE DATABASE, CREATE TABLE, ALTER TABLE, etc. The most used DDL commands are CREATE, DROP, ALTER, and TRUNCATE.

• CREATE
  CREATE command is used to create a database and database object like a table, index, view, trigger, stored procedure, etc.
  Syntax
  CREATE TABLE Employee (Id INT, Name VARHCAR(50), Address VARCHAR (100));
• ALTER
  ALTER command is used to restructure the database object and the settings in the database.
  Syntax
  ALTER TABLE Employee ADD Salary INT;
• TRUNCATE
  The TRUNCATE command is used to remove all the data from the table. TRUNCATE command empties a table.
  Syntax
  TRUNCATE TABLE Employee;
• DROP
  DROP command is used to remove the database and database object.
  Syntax
  DROP TABLE Employee;

DML

DML stands for data manipulation language. DML commands are used for manipulating data in a relational database management system. DML commands are used for adding, removing, updating data in the database system, like INSERT INTO TableName, DELETE FROM TableName, UPDATE tableName set data, etc. The most used DML commands are INSERT INTO, DELETE FROM, UPDATE.