How to do Subqueries in SQL with Examples

Step-by-step tutorial shows you how to use SQL subqueries in your SELECT statement & FROM and WHERE clauses!

Queries:
1) A subquery in the SELECT statement: SELECT customerid, freight, (SELECT AVG(freight) FROM orders) FROM orders
2) A subquery in the FROM clause: SELECT shipcountry, AVG(num_orders) FROM (SELECT customerid, shipcountry, count(*) AS num_orders FROM orders GROUP BY 1,2) sub GROUP BY 1
3) A subquery in the WHERE clause: SELECT * FROM orders WHERE employeeid IN (SELECT employeeid FROM employees WHERE LOWER(firstname) LIKE '%b%')

Support the Channel:

[honeyclover]

Finally, a break through. Finally, someone who explains the use of sub queries well.

[dabeast]

CANNOT EXPLAIN ENOUGH HOW MUCH YOU SAVED MY LIFE.

[kristiankelloway]

The idea that a subquery in a FROM statement creates a table and starting the query process from there was a real lightbulb moment - thank you

[sarahemslie]

This is really helpful; more so than my online course! I look forward to watching more of your videos. Thank you!

[Aaron-ilpk]

Thank you for telling us that even when you first learned this it was complex, because holy cow! I cannot wrap my head around this. I can kind of grasp whats going on, but I think you know the confusion that goes through a noob's mind. Thank you for your tutorials! I plan on watching many more of your videos.

[dfgndfghdfghdfgh]

super helpful and you explain stuff in a way where you don't rush through it but also don't take ages on it.

[Peter-cxir]

Really great explanations. Easy to follow and perfect variety. Very much appreciate you posting these tutorials, they're beyond helpful. Thanks!

[juliakristavilladiego]

Spending my Christmas binge watching your SQL tutorials haha so helpful. Thank you!!!!

[cameronp]

Great video man!
The best explanation of sub queries that I found!
This is helping me a lot because I'm starting with a course of T-SQL

[jorgehernandezdominguez]

WOW! the way you explained that is like first doing a table to then going and making a query from that table was a breakthrough for my understanding of the concept. I really admire people who can transform concepts into more digestible material. Thanks

[kramoo]

Absolutely amazing explanation and you give hope that you said it took you a while, now look at you.

[AlexMar-r]

So easy to understand without broken English. Keep them coming!

[goptefq]

Thank you for explaining it the way you did, it just clicked for me. Great stuff! Keep up the good videos.

[mmoralls]

Great video! Thank you so much for bringing a clear explanation of this topic. I look forward to viewing your other videos.

[samuelopoku-acheampong]

Thanks for the tutorials, you have being of great help on this journey...Keep them coming

[kw]

Just started a Business Systems Analyst entry level position that uses SQL everyday and this video has been so helpful! You explained it better than the corporate instructor, Khan Academy and my Udemy course! THANK YOU!!!!

[jcopas]

This was very helpful. It saved me a lot of time. I understood it the first viewing and was able to apply the concepts with ease and complete my homework on time. Thank you, you do an excellent job. I will come back for future questions in SQL.

[manaygun]

Simple and direct. Just what I was needed.

[andyn]

great videos! Its soo much easier too understand when watching your tutorials! Please do more advanced videos with window functions etc.

[davidcoley]

A great, and much needed take on this subject.