SQL Window Functions: The Key to Succeeding in Data Science Interviews

Window functions are a part of SQL that is useful on a daily basis for data scientists. This video will give you an overview of SQL window functions by explaining:
- When are window functions
- Syntax of window function
- How to define a window
- How to select a function

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Contents of this video:
====================
00:00 What is a Window Function
02:28 Syntax of Window Functions
03:23 Define a Window Frame using Over Clause
04:00 PARTITION BY
04:50 ORDER BY
05:23 ROWS/RANGE
08:35 Aggregate Functions
09:11 Ranking Functions
11:16 Analytic Functions

[raquelc.]

This is the best video about window functions that I have seen so far! Wow! Congrats and thanks!

[QuantumImperfections]

WAS FANTASTIC! I've got 4+ years of experience in SQL and I needed a quick refresher for window functions and this was exactly what I needed. Thank You!

[krishnamvats]

stopped in between of the video, the best part about the video is that it explains the difference between group by and window function. This is something not many youtuber do. I was struggling to visualize how it happens. Thanks a lot

[danielkoo]

Thanks Emma for sharing. What you shared helped me comprehend window functions. Most importantly, I applied those window functions to my day to day work, which boosted efficiency. Appreciated :)

[austinbai]

This is the best vedio talking about window fundction on Youtube, thanks Emma! Please keep up the great work!

[xiaomengwu]

Your channel is the best on all DS interviews! well organized, clear and short!

[alienfunbug]

This video is so condensed and packed full concise and well explained materials. Thank you for the fantastic content.

[LorenzoAnderson-ihke]

Super clear and orginised, thank you!!! 👍

[swastikchowdhury]

This was very helpful. Beautiful content <3

[FelipeCampelo]

I have been storing so many CTEs using the WITH statement lol. I think these window functions could make my queries less verbose.

Great content!

[sw]

Emma luv u. Your explanations are very elaborative and succinct at the same time.

[maweryoutube]

Very clear, detailed, and amazing explanation
SUBSCRIBED from more great videos adventure
Thank you

[AVChian]

Great lecture!!! Exactly what I was looking to solve my problem at work. I am definitely subscribing to your channel.

[djjiang]

Hello Emma, your videos are superb and great and very useful! Just one thing, we can use negative value when we use LEAD or LAG, basically lead(date, -1) over (order by date) equivalent of lag(date, 1) over(order by date), which I tested in PostgreSQL and Snowflake, and they both works.

[kirusha_kras]

Emma, your content is great. Your English is beautiful and clear. My respect

For subscribers:
I would like to use the comments to find ways to improve my English. If you are starting your journey in data analytics and you are a native speaker of English, we can be useful to each other) For example, weekly calls or something similar
Best regards, Senior Data Analyst from Russia

[ashleyblanchard]

Hi Emma, what app do you use to record yourself and the screen?

[nishantjain]

Shouldn't the SUM() at 9:09 do a cumulative sum since order function is mentioned ?

[stonewatertx]

Great video! One quick question: At 9:10, I thought SUM(value) OVER(ORDER BY value) will return cumulative sum; but SUM(value) OVER() ORDER BY value will return the SUM shown in the video. or is it a PostgreSQL thing? I'm a little confused now.

[stonewatertx]

Sorry for another dumb question: I tried something like "select rank(a) over(order by a) from t" in PostgreSQL. It'll show error telling me to add WITHIN GROUP. But if I write "select rank() over(order by a) from t" then it's fine. Seems like I can't pass anything in the () after rank. Could anyone clarify?

[iedmzcp]

Emma: How are you? I am from Brazil. Do you have a video about partitions and frames?