SQL Tutorials : Basics to Advanced Concepts 2024

SQL, or Structured Query Language, serves as the backbone for managing data in databases across various systems like MySQL, SQL Server, MS Access, Oracle, Sybase, Informix, Postgres, and more. In this tutorial, we'll delve into the fundamental aspects of SQL, exploring its syntax, key commands, and the role it plays in relational database management.

"In SQL, we trust. The power to query, the ability to manage, the essence of relational databases."
- SQL Devotee (source)

Understanding SQL

SQL, short for Structured Query Language, is a versatile language designed for accessing, manipulating, and retrieving data in databases. It stands as an ANSI (American National Standards Institute) standard, ensuring a consistent approach to interacting with databases.

"SQL: Bridging the gap between data chaos and organized insights. A language that speaks volumes without saying much."
- Query Sage (source)

What Can SQL Do?

SQL empowers users to perform a myriad of operations on databases:

• Execute queries on databases (SELECT).
• Insert records into databases (INSERT INTO).
• Update records in databases (UPDATE).
• Delete records from databases (DELETE).
• Create new tables in databases (CREATE TABLE).
• Create stored procedures in databases.
• Create views in databases.
• Set permissions for tables, procedures, and views in databases.(Permissions in SQL oracle example)
• Retrieve data with more power from databases. (SQL SELECT INTO)

"SQL: The language that turns data into information, databases into insights, and coders into data maestros."
- Data Whisperer (source)

SQL is a Standard, But…

Despite adhering to ANSI standards, SQL comes in different versions. For compliance, a minimum support for essential commands like SELECT, UPDATE, DELETE, INSERT INTO, WHERE, etc., is necessary.

"A well-crafted SQL query is like a finely tuned symphony, orchestrating the harmony of data."
- Database Composer (source)

RDBMS - The Foundation

At the core of modern database systems lies RDBMS (Relational Database Management System), forming the foundation for SQL, MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access. Data in RDBMS is stored in objects called tables, comprising columns and rows.

"SQL, I acknowledge your ubiquity and know that no relational database can thrive without your expressive queries."
- some-said (source)

SQL Syntax

Database Tables

Databases typically contain one or more tables, each identified by a name (e.g., ‘Customers’ or ‘Orders’). Tables house records (rows) with data. This tutorial uses the well-known Northwind sample database (included in MS Access and MS SQL Server) as an example.

Below is a selection from the “Customers” table:

"SQL is the art of asking the right questions to unveil the story hidden within the tables and rows."
- Data Storyteller (source)

SQL Statements

Most operations in a database are performed using SQL statements. The following SQL statement selects all records from the Customers table:

SELECT * FROM Customers;

Customers Table Sample

"To SQL or not to SQL? That is never the question. It's always the answer."
- SQL Shakespeare (source)

Important Notes

• SQL keywords are case-insensitive: select is the same as SELECT.
• All SQL keywords in this tutorial are written in uppercase.

"SQL is the magic wand in the hands of a data wizard, turning bits and bytes into actionable intelligence."
- Data Magician (source)

The Purpose of the Semicolon ; After SQL Statements

In some database systems, a semicolon is required at the end of each SQL statement. The semicolon serves as a standard way for the database system to distinguish each SQL statement in the same call to the server, allowing the execution of multiple SQL statements in one call.

This tutorial uses a semicolon at the end of each SQL statement.

"SQL: Where precision meets power, and queries transform data into decisions."
- Query Alchemist (source)

Key SQL Commands

• SELECT: Extracts data from a database.
• UPDATE: Updates data in a database.
• DELETE: Deletes data from a database.
• INSERT INTO: Inserts new data into a database.
• CREATE DATABASE: Creates a new database.
• ALTER DATABASE: Modifies a database.
• CREATE TABLE: Creates a new table.
• ALTER TABLE: Modifies a table.
• DROP TABLE: Deletes a table.
• CREATE INDEX: Creates an index (search key).
• DROP INDEX: Deletes an index.

"SQL is the thread that weaves the fabric of coherent and meaningful databases."
- Data Weaver (source)

For more in-depth SQL tutorials, you can visit:

• 5 Types of SQL Database Commands

• AS Alias SQL Tutorial: Aliases to Enhancing Database Query Readability

• Connect SSIS to Azure SQL Database

• Connect to Azure SQL Database from SSMS

• Full SQL Tutorial for Beginners

• How to Learn SQL Databases in 2023

• Importance of SQL for Data Analysis

• SQL AND, OR, NOT Operators

• SQL ANY and ALL

• SQL BETWEEN Operator

• SQL COALESCE Function: Handling Null Values

• SQL COUNT, AVG, SUM

• SQL DELETE

• SQL EXISTS

• SQL GROUP BY

• SQL HAVING

• SQL IN Operation

• SQL INSERT INTO

• SQL INSERT INTO SELECT

• SQL Introduction

• SQL JOINS

• SQL LIKE Operator

• SQL MIN, MAX

• SQL NULL

• SQL ORDER BY Keyword

• SQL SELECT

• SQL Techniques for Data Analysis

• SQL TOP, LIMIT, ROWNUM

• SQL UNION

• SQL UPDATE

• SQL WHERE

• SQL Wildcards

• Top 10 Practices for Azure SQL Databases

• Use Datatypes in Oracle

• What Are Basics? Advance SQL Cheatsheet

• What Are Triggers in SQL

• What Is CTE in SQL

• What Is Stored Procedure in SQL

• What Is Trigger in SQL

For MySQL-specific tutorials, you can visit:

• Connect MySQL Server to VSCode
• Getting Started with MySQL in VSCode
• Install MySQL for VSCode
• Introduction to MySQL
• Load Sample Database (Employees DB) in VSCode
• MySQL Aliases in VSCode
• MySQL AND Operator in VSCode
• MySQL BETWEEN Operation in VSCode
• MySQL DISTINCT in VSCode
• MySQL IN Operator in VSCode
• MySQL IS NULL Operator in VSCode
• MySQL JOINS in VSCode
• MySQL LIKE Operator in VSCode
• MySQL LIMIT in VSCode
• MySQL NOT IN Operator in VSCode
• MySQL OR Operator in VSCode
• MySQL ORDER BY in VSCode
• MySQL SELECT FROM in VSCode
• MySQL WHERE in VSCode
• Sample Database (Employees DB) for MySQL in VSCode