SELECT basics - SQLZoo

The example uses a WHERE clause to show the population of 'France'. Note that strings should be in 'single quotes';

sqlzoo.net

Learn SQL - Online SQL Terminal - Practice SQL Querys

Practice SQL querys with an online terminal. Solve SQL query questions using a practice database. Learn and improve your SQL skills.

www.sql-practice.com

SQL 50 - Study Plan - LeetCode

Crack SQL Interview in 50 Qs

leetcode.com

PostgreSQL Exercises

Welcome to PostgreSQL Exercises! This site was born when I noticed that there's a load of material out there to help people learn about SQL, but not a great deal to make it easy to learn by doing. PGExercises provides a series of questions and explanations built on a single, simple dataset. It's designed for use as a partner to a good book or Postgres' excellent documentation.

pgexercises.com

Solve Programming Questions | HackerRank

A special-purpose language designed for managing data held in a relational database.

www.hackerrank.com

SQL Index

Module 1: MySQL Into Query

1. SQL Subdivisions
• Data Definition Language (DDL)
• Data Manipulation Language (DML)
• Data Control Language (DCL)
• Transaction Control Language (TCL)
• Data Query Language (DQL)
2. SELECT FROM
• MySQL SELECT FROM statement
3. SQL ORDER BY
• Using ORDER BY clause to sort the result set by one column example
• Using the ORDER BY clause to sort the result set by multiple columns example
• Using the ORDER BY clause to sort a result set by an expression example
• Using MySQL ORDER BY clause to sort data using a custom list
• MySQL ORDER BY and NULL
4. SQL Where
• Using the WHERE clause with operator example
• Using the WHERE clause with the AND operator
• Using the WHERE clause with OR operator
• Using the WHERE clause with the BETWEEN operator
• Using the WHERE clause with the LIKE operator example
• Using the WHERE clause with the IN operator example
• Using the WHERE clause with NOT IN operator
• Using the WHERE clause with the IS NULL operator
• Using MySQL WHERE clause with comparison operators
• Using MySQL DISTINCT clause
• Using MySQL LIMIT clause
5. SELECT INTO Variable
• MySQL SELECT INTO variable

Module 2: MySql Joining

1. DATABASE SCHEMA
• ERD Design and Notation
• To One (|)
• To Many (<)
• To One and Only One (||)
• To One or Many (|<)
• To Zero or Many (O<)
2. TABLE RELATIONSHIP
• Many-to-Many, 
• Many-to-One, 
• One-to-Many
• One-to-One.
3. TABLE AND COLUMN ALIAS
• Column aliases
• Table aliases
4. JOIN
• inner Join
• Left Join
• Right Join
• Self Join
• Cross Join

Module 3: MySql Grouping Data

1. AGGREGATE FUNCTIONS
2. MYSQL GROUP BY Clause
• Example 1:  Basic MySQL GROUP BY example
• Example 2: Using MySQL GROUP BY with aggregate functions
• Example 3:  MySQL GROUP BY with expression example
• Example 4:  Using MySQL GROUP BY with HAVING clause example
• Example 5: Grouping by Multiple Columns
• Example 6: The GROUP BY clause vs. DISTINCT clause
3. MySQL HAVING clause
• Example 1: A Simple HAVING COUNT Query
• Example 2: Practical HAVING with COUNT