SQL Server - Introduction to SQL

 Introduction to SQL 

SQL is a standard language for accessing and manipulating databases. SQL stands for Structured Query Language. SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987.

It is used for storing and managing data in relational database management system (RDMS). It is a standard language for Relational Database System. It enables a user to create, read, update and delete relational databases and tables

Using the SQL statements, you can perform most of the actions in a database.

Structured Query Language (SQL) is a standard query language that is used to work with relational databases.

We use SQL to

·         Create databases

·         Create tables

·         Read data

·         Insert data

·         Update data

·         Delete data

·         Delete database tables

·         Delete databases

SQL code is divided into four main Categories

1.   SELECT Statement – SELECT Query used to extract data from multiple table. Clauses such as WHERE, FROM, ORDER BY etc used to extract specific/conditional data from the tables

2.      DML – Data manipulation Language is used to INSET, DELETE, UPDATE data to table.

3.    DDL – Data Definition Language is used for managing tables and index structures. Examples of DDL statements include CREATE, ALTER, TRUNCATE and DROP.

4.    DCL – Data Control Language is used to assign database rights and permissions. Statements used are GRANT and REVOKE.

Types of DBMS

There are two types of databases:

Relational

In RDBMS, data is stored in tabular format.  Examples for RDBMS MySQL, PostgreSQL, MSSQL, Oracle etc

Non – Relational

Data Is Stored in Key-Value Pairs. Examples for Non – RDBMS MongoDB, Amazon DynamoDB, Redis, etc