What is SQL and its example?

A database is an organized collection of data so that it can be easily accessed. To manage these databases, Database Management Systems (DBMS) are used.

Types of DBMS

In general, there are two common types of databases:

Non-Relational Database Management System (Non-RDBMS)

In Non-RDBMS, data is stored in key-value pairs. For example:

Here, customers' data are stored in key-value pairs.

Commonly used Non-RDBMS: MongoDB, Amazon DynamoDB, Redis, etc.

Relational Database Management System (RDBMS)

In RDBMS, data is stored in tabular format. For example,

Here, customers is a table inside the database.

The first row is the attributes of the table. Each row after that contains the data of a customer.

In RDBMS, two or more tables may be related to each other. Hence the term "Relational". For example,

Here, orders and customers are related through customer_id.

Commonly used RDBMS: MySQL, PostgreSQL, MSSQL, Oracle etc.

Note: To access data from these relational databases, SQL (Structured Query Language) is used.

Introduction to SQL

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 in a database
• read data from a table
• insert data in a table
• update data in a table
• delete data from a table
• delete database tables
• delete databases
• and many more database operations

SQL Example: Read Data From a Table

Let's take a look at an example,

SELECT first_name, last_name FROM Customers;

Here, this SQL command selects the first name and last name of all customers from the customers table.

SQL is used in all relational databases such as MySQL, Oracle, MSSQL, PostgreSQL etc.

Note: The major SQL commands are similar in all relational databases. However, in some cases, SQL commands may differ.

In this SQL tutorial series, we will learn about SQL in detail. We will cover any SQL command differences among MySQL, Oracle, SQL Server, Postgres, and other commonly used database systems.

SQL is a language to operate databases; it includes database creation, deletion, fetching rows, modifying rows, etc. SQL is an ANSI (American National Standards Institute) standard language, but there are many different versions of the SQL language.

What is SQL?

SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in a relational database.

SQL is the standard language for Relational Database System. All the Relational Database Management Systems (RDMS) like MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their standard database language.

Also, they are using different dialects, such as −

• MS SQL Server using T-SQL,
• Oracle using PL/SQL,
• MS Access version of SQL is called JET SQL (native format) etc.

Why SQL?

SQL is widely popular because it offers the following advantages −

• Allows users to access data in the relational database management systems.

• Allows users to describe the data.

• Allows users to define the data in a database and manipulate that data.

• Allows to embed within other languages using SQL modules, libraries & pre-compilers.

• Allows users to create and drop databases and tables.

• Allows users to create view, stored procedure, functions in a database.

• Allows users to set permissions on tables, procedures and views.

A Brief History of SQL

• 1970 − Dr. Edgar F. "Ted" Codd of IBM is known as the father of relational databases. He described a relational model for databases.

• 1974 − Structured Query Language appeared.

• 1978 − IBM worked to develop Codd's ideas and released a product named System/R.

• 1986 − IBM developed the first prototype of relational database and standardized by ANSI. The first relational database was released by Relational Software which later came to be known as Oracle.

SQL Process

When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task.

There are various components included in this process.

These components are −

• Query Dispatcher
• Optimization Engines
• Classic Query Engine
• SQL Query Engine, etc.

A classic query engine handles all the non-SQL queries, but a SQL query engine won't handle logical files.

Following is a simple diagram showing the SQL Architecture −

SQL Commands

The standard SQL commands to interact with relational databases are CREATE, SELECT, INSERT, UPDATE, DELETE and DROP. These commands can be classified into the following groups based on their nature −

What is an example of a SQL database?

What is SQL in short answer?

What are the 5 types of SQL?

What are the 3 types of SQL commands?