Subqueries Courses

How to Transform Tables with SQL
Codecademy

Google BigQuery & PostgreSQL : Big Query for Data Analysis
Udemy

Get Started Querying with Transact-SQL
Microsoft via Microsoft Learn

SQL: Using Joins, Constraints, Normalization, and Subqueries (Interactive)
Pluralsight

Java Data Access - SQL Primer
LearnQuest via Coursera

Oracle SQL Exam Prep
LearnQuest via Coursera

The Structured Query Language (SQL)
University of Colorado Boulder via Coursera

Microsoft SQL Server 2012 Certification Training Exam 70-461
Udemy

Microsoft Access SQL: SQL for Non-Programmers
Udemy

Master SQL For Data Science
Udemy