Complex SQL Query Breakdown Step By Step

📝 Get my free SQL Cheat Sheets: www.databasestar.com/get-sql-...
🎓 Learn and become confident in SQL: databasestar.mykajabi.com/sql...
When you work with SQL you may come across a query that seems quite complex. It could have many tables and joins, many columns, functions, subqueries, and more features you may or may not have heard of.
In this video, I'll show you how to understand a complex query. We will
- start with a complex SQL query
- improve the formatting of it
- create a diagram of the tables and columns
- run parts of the query
- add comments
At the end of this process, we'll be able to understand and describe what the query does.
You can follow this kind of process for your own complex query.
⏱ TIMESTAMPS:
00:00 Intro
00:40 Our query
01:31 Formatting the query
02:51 Create a diagram
09:46 View the table data
11:01 Run subqueries
12:38 Add comments
13:38 Run the main query
🔗 VIDEO LINKS:
Sample SQL: github.com/bbrumm/databasesta...

[@baruchben-david4196]

I have to say that your explanations are clear and informative, well-organized. Thank you. You've helped break a difficult subject into bite-sized pieces I can handle.

[@DatabaseStar]

Thanks very much for the kind words! That’s what I am aiming for with my videos, so it’s good to hear it’s been achieved!

[@maxyudin]

I'm self-taught in SQL, and I use simple queries because that's all I need to achieve my goals. But I've missed this kind of explanation in my past when I googled tutorials that were faintly intelligible and confusing. Been subscribed for a while now and have watched a couple dozen of your videos. Thanks for your work!

[@DatabaseStar]

Thanks for sharing, glad you found my videos helpful!

[@punkyM637]

Thank you for all your videos!! I thoroughly enjoy them

[@DatabaseStar]

No problem, glad you like them!

[@WestCoastKop]

Fantastic tutorial, it's really helpful to understand how to break down the subqueries and visualize each table/column

[@DatabaseStar]

Thanks, glad you found it helpful!

[@kvanniekerk3792]

Brilliant explanation, thank you. I have recently started getting more invested in understanding data and how SQL works to aid that journey. Complex queries have till now intimidated me, but your explanation made perfect sense and is actually a logical yet simple way to decompose a complex query to its constituent parts. Thank you indeed. I was thinking of using a UML diagram to replace your diagram boxes as then I can see the structure clearer.

[@DatabaseStar]

Thanks for the comment! I'm glad you found it helpful. A UML diagram would also be helpful as you suggested.

[@patyue5012]

Nice content! Thanks.

[@DatabaseStar]

Glad you like it!

[@sabuein]

Thank you.

[@DatabaseStar]

You're welcome!

[@oracle_professor]

Excellent work Database Star

[@DatabaseStar]

Thanks!

[@attaullahkhan2504]

Kindly make more videoa like this... thanks in advance.

[@DatabaseStar]

Thanks, sure I can do that.

[@kumarmv-lo1rm]

I was looking for something like this. This really helps. Thanks. Is it possible to do one with the with clause and unions and joins all together.

[@DatabaseStar]

Glad it's helpful! Sure I can do one with a with clause, unions, and joins.

[@jorso163]

Sir,when i am exporting data i couldn't see the ongoing exporting details in Oracle SQL developer like how many rows exporting is going on like this and how to enable this ,please help me

[@DatabaseStar]

I'm not sure why that would be happening. I assume it's something that should happen by default.

[@rustyspottedcat8885]

Its all about ... sets of all sets ... that doesnt contain themselves.

[@DatabaseStar]

That's a good point!

[@ai-oo9ls]

i just started learning sql, i want to ask when should i use procedure ?

[@DatabaseStar]

I've got another video on using stored procedures on my channel, ("Store procedures are better than raw SQL") which has some more detail, but there are a few advantages: easier design if there are many people or applications accessing a database, better to handle complex logic that can't be done in a regular SQL statement.

[@Learn_IT_with_Azizul]

very important content but sound is so low... plz have a look. ty

[@DatabaseStar]

The sound seems fine in this video when i compare it to other videos on KZbin. My older videos had low sound because my old microphone but this one should be OK.

[@Myself_9037]

I have a doubt. I have table with two fields, one field is array in table 1 uID | Contact 2 | 1221,1223 3 | 1123 Now value of 1221 and 1223 are in table Two. I want a query to join table 1 and table 2 using array of field2

[@DatabaseStar]

I'm not sure I fully understand the issue, but I think you could join the two tables together based on common values.