Our training courses

Book any course as classroom, onsite or online training, or as one-to-one consultancy
Excel Training Basic Excel Advanced Excel VBA Macros Office Scripts Excel Introduction Excel Intermediate Excel Advanced Excel Business Modelling Excel VBA macros Advanced VBA Fast track Excel VBA Basic Office Scripts Advanced Office Scripts Power Platform Training Pure Power BI DAX and fast-track Power Automate Power Apps Introduction to Power BI Adv. Power BI Reports Adv. Power BI Data DAX for Power BI Fast track Power BI Fast track Power BI/DAX Power Automate Desktop Basic Power Automate Advanced Power Automate Fast track Power Automate Power Apps Programming and AI SQL training Visual C# training Python training AI training Introduction to SQL Advanced SQL Fast track SQL Introduction to MySQL Introduction to Visual C# Intermediate C# Fast track C# Introduction to Python Advanced Python Fast track Python Using AI tools Using the OpenAI API SQL Server training Reporting Services Report Builder Integration Services Azure / SSAS Reporting Services Advanced SSRS Fast track SSRS Report Builder Introduction to SSIS Advanced SSIS Fast track SSIS SQL in Azure Data Studio SSAS - Tabular Model
Other training resources

Free resources

Read our blogs, tips and tutorials

Try our exercises or test your skills

Watch our tutorial videos or shorts

Take a self-paced course

Read our recent newsletters

Paid services

License our courseware

Book expert consultancy

Buy our publications

Getting help

Get help in using our site
Our training venues

Where we are

London

Manchester

Where you are

Across the UK

At your site

Online

At your computer
Why we are different

Transparent reviews

551 attributed reviews in the last 3 years

Delivery of courses

Refreshingly small course sizes

Outstandingly good courseware

Whizzy online classrooms

Wise Owl trainers only (no freelancers)

Nicer to work with

Almost no cancellations

We have genuine integrity

We invoice after training

Reliable and established

Review 30+ years of Wise Owl

View our top 100 clients

Search our website

GO
+44 (161) 883 3606 sales@wiseowl.co.uk Web enquiry form
We also send out useful tips in a monthly email newsletter ...

Sign up to newsletter

Our training courses

AI - Articial Intelligence

Power BI and DAX

Other training resources

Tips and tricks

Guides and tutorials

YouTube tutorials

Test your skills

Self-paced courses

Our training venues

Why we are different

Hundreds of published reviews

Small class sizes

Outstanding courseware

Online classroom

(Almost) no cancellations

Wise Owl trainers only

Genuine integrity

Invoices after training

30+ years of Wise Owl

Our top 100 clients

This page has 1 thread | Add post

Video tutorials

Video tutorials

Finding our videos useful? Please consider helping us to share more!

Selecting data in SQL videos | SQL Queries Part 12 - Correlated Subqueries

Posted by Andrew Gould on 31 October 2012

SQL Queries Part 12 - Correlated Subqueries

A correlated subquery is a subquery which depends on an outer query for its values. If that doesn't make much sense, this video attempts to explain exactly what that means. You'll see how to build simple correlated subqueries, including why it's necessary to use table aliases, along with an explanation of what happens when you execute the query.

See our full range of SQL training resources, or test your knowledge of SQL with one of our SQL skills assessment tests.

This video has the following accompanying files:

File name	Type	Description
Create Movies Database with Genre Table.sql	SQL query
GenerateMoviesDatabase.sql	SQL query
GenerateUpdatedMoviesDatabase.sql	SQL query

Click to download a zipped copy of the above files.

There are no exercises for this video.

Making a video bigger

You can increase the size of your video to make it fill the screen like this:

Full screen view

Play your video (the icons shown won't appear until you do), then click on the full screen icon which appears as shown above.

When you've finished viewing a video in full screen mode, just press the Esc key to return to normal view.

Improving the quality of a video

To improve the quality of a video, first click on the Settings icon:

Settings icon

Make sure yoiu're playing your video so that the icons shown above appear, then click on this gear icon.

Choose to change the video quality:

Changing video quality

Click as above to change your video quality.

The higher the number you choose, the better will be your video quality (but the slower the connection speed):

Different speeds

Don't choose the HD option shown unless your connection speed is fast enough to support it!

Is your Wise Owl speaking too slowly (or too quickly)? You can also use the Settings menu above to change your playback speed.

This page has 1 thread

From:	Sanka
When:	07 Apr 21 at 10:17

Hello Wise Owls,

I do have a question regarding the last case.

If the code in Line 14 is removed, will the output stays the same pls? Since the output is ORDERED BY y, we will always find the results rank by year, right?

Thanks in advance,

Sanka

From:	Andrew G
When:	12 Apr 21 at 07:39

Hi Sanka,

No, the results would be different if you remove line 14 from the last example. Line 14 is what makes this a correlated subquery. Without that line your results would return any film whose run time is longer than the average run time of every film in the table. With line 14 your results return each film whose run time is longer than the average run time of only those films made in the same year.

We aren't ranking results in this example, the ORDER BY clause was added simply to see the results more easily.

I hope that helps!

Reply

Reply

Head office

Kingsmoor House

Railway Street

GLOSSOP

SK13 2AA

London

Landmark Offices

99 Bishopsgate

LONDON

EC2M 3XD

Manchester

Holiday Inn

25 Aytoun Street

MANCHESTER

M1 3AE

Visual C# training

Excel training courses

Power Automate training

Power BI / DAX training

Python training courses

SQL training courses

VBA (macros) training

© Wise Owl Business Solutions Ltd 2024. All Rights Reserved.

Terms & Conditions

End of small page here

Please be aware that our website uses cookies!

I'm OK with this Tell me more ...