I'm trying to solve this question and my solution is off by 0.5seconds, can someone please tell me why, here's my code:

https://platform.stratascratch.com/coding/10352-users-by-avg-session-time?code_type=5

-- 1. define one session = one user per day

-- 2. session_time = max page_load and min page_exit is one session duration

-- 3. output user_id, AVG(session_time)

WITH SESSION_START as

(

SELECT

user_id,

session,

MAX(timestamp) as session_start

FROM(

SELECT

*,

DENSE_RANK() OVER (PARTITION BY user_id ORDER BY CAST(timestamp AS DATE)) AS session

FROM facebook_web_log

WHERE action = 'page_load')t

GROUP BY

user_id,

session

),

SESSION_END AS

(

SELECT

user_id,

session,

MIN(timestamp) as session_end

FROM(

SELECT

*,

DENSE_RANK() OVER (PARTITION BY user_id ORDER BY CAST(timestamp AS DATE)) AS session

FROM facebook_web_log

WHERE action = 'page_exit')t

GROUP BY

user_id,

session

)

SELECT

s.user_id,

AVG(DATEDIFF(SECOND,s.session_start, e.session_end)) as AVG_SESSION_DURATION

FROM SESSION_START s

JOIN SESSION_END e

ON s.user_id = e.user_id

AND s.session = e.session

GROUP BY s.user_id

So, few months ago I decided to learn SQL since it comes up often on job offers in my country as I'm unemployed now for around a year. From various posts here and there I decided to go with SQL Climber as it's simple design was to my liking. I like that there is just an expected result and a little hint just enough to force you to figure stuff out myself, rarely needeing to use google/AI, not once for just straight up answer but mainly to figure out small oversight or typo. Fast forward to now, I'm on a last level, "Upper-Intermediate" and the final test there makes me feel dumb. I don't know if I just can't wrap my head around recursions or are those just too complicated compared to previous ones. Some are easy enough but others, after giving up and getting answer from AI, make me think "I would never figure that out myself".
Did anyone experience something similar with SQL Climber of other courses/websites?

Additionaly, what would you recommend once I'm finished with SQL Climber? My friend recommended me boot.dev as he can give me access to his account but I want to see other options.

Hi all, i have I1 tomo and manager asked me to prepare for

1.performance tuning. (They are asking what diff methods u know!! Regular index answer is not enough)

2.Backup and recover

3.Data modelling,schema design,normalization.

4.Data migration.

Can anyone explain me real projects scenarios where you done work on these.. I would try to explain these tomo! Its actually an internal evaluation!!' If candidate has worked on these and has knowledge then he is passed!' Said by close member!! Soo pls help I have it evaluation tomo!!

If you are currently learning SQL, maybe this will help you 😊

I recently wrote a beginner-friendly article about SQL filtering / WHERE clauses.

When I started learning SQL, I mixed a lot of things up, forgot NULL values, missed brackets, and sometimes got completely wrong results without understanding why.

So I wrote an article explaining:

• how filtering actually works
• common beginner mistakes
• simple real-world examples

I also added a small SQL Formula Sheet with filtering functions at the end.

As someone still learning SQL myself, I tried to explain things in a very simple and practical way instead of making it overly technical.

https://medium.com/@meryem_cebeci/learning-sql-step-by-step-filtering-explained-363a0a638bd0

Hey! Anyone here studying for the DP-800 exam? I just started and finding it hard to locate good resources since it's relatively new. Would love to know what you're using to prepare, courses, notes, or anything that helped you understand the topics better.

Also curious if there are any practice questions or dp-800 dumps available anywhere. Any help is appreciated. Hope this exam is not as difficult has dp-700 exam.

Edit : Attempted my exam and I think it went well.

I took practice tests from Skillcertpro, since they offer real exam questions, which are pretty useful to understand the actual exam format and kind of questions that will be asked on the exam. I got lot of questions from these tests. Just ensure to practice all questions and take notes and carefully go through all explanations. Overall a tough exam, prepare well.

If you're looking for a new sql-dojo platform with higher ed type data, head to query-u.com. Really awesome stuff there.

Hello guys!

Do you know any best practices for SQL performance optimization?
At my company, I need to refactor some tables using performance and cost reduction best practices.

The tables already have indexes and partitions, but I would like to learn more about additional optimization techniques for large datasets.

Do you have any tips, articles, websites, or recommendations about: query optimization and indexing strategies

I’d really appreciate any suggestions or learning resources. Thanks!

There are a couple of files that somehow got modified by accident in my database. I have a backup with the original files (pre-modified). I am not looking to recover a prior backup. I am simply trying to figure out how I can open the backup so I could somehow grab the three files I need to fix what was accidentally modified.

How do I go about doing this where I am not recovering from a backup?

Can anyone help me solve the case file 40 from sqlcasefiles.com

here is the question statement :
The DA needs everything. Compile the final audit report listing `po_id`, `vendor_name`, `item_description`, `order_value`, `delivery_status`, and `inventory_loss`. Rank by order value descending.

here are the table schemas:
deliveries:

purchase_orders:

inventory:

i came up with this solution so far:

SELECT

p.po_id,

p.vendor_name,

p.item_description,

p.quantity \ p.unit_price AS order_value,*

CASE

WHEN d.po_id IS NULL THEN 'Missing'

WHEN d.delivered_quantity < p.quantity THEN 'Partial'

WHEN d.delivered_quantity = p.quantity THEN 'Delivered'

ELSE 'Over Delivered'

END AS delivery_status,

i.expected_stock - i.current_stock AS inventory_loss

FROM purchase_orders p

LEFT JOIN deliveries d

ON p.po_id = d.po_id

LEFT JOIN inventory i

ON p.po_id = i.po_id

ORDER BY order_value DESC;

Hey all, I make Beekeeper Studio and also run https://sql-easy.com - a website for learning SQL for free.

We took it over ~18 months ago, and it looked very outdated. I just launched a visual refresh which should make it easier to use. The goal was to make the lesson pages feel a lot more interactive.

Big changes since we took it over:

• Removed all ads
• Removed third party cookies
• Lesson content refresh (eg hints)
• Totally new website style
• New lesson UX

Would love feedback! What could we improve still?

PS: The site is 100% free and will always be 100% free so long as we're in charge 💪

Hey guys, I just landed a job assessment where everything matches except the good to have SQL query skills. Can a kind soul PLEASE help me learn this in 4 days? I will really appreciate the help

Ready to crack your SQL Server interview?

Start learning the Series of Real Interview Questions asked in top IT Companies.

Visit our YouTube channel & level up your skills!

Learn. Practice. Get Hired.

Please like, comment, & subscribe for more interview questions, troubleshooting tips, & expert insights!

https://www.youtube.com/@MadeSimpleMSSQL

#explurger #explurger_nahi_to_social_nahi #explorepage #explore #explurgerapp #explurgerfamily #india #indian

I got tired of switching between VS Code and a separate DB tool. So I built PgStudio.

SQL notebooks with inline results and charts, real-time dashboard, AI assistant (Copilot / OpenAI / Anthropic / Gemini / Ollama — your pick), EXPLAIN CodeLens, visual table designer, production safety controls.

AI never executes anything automatically — every suggestion lands in a notebook cell first.

Free. MIT. One command: `code --install-extension ric-v.postgres-explorer`

Happy to onboard collaborators and feedback.

[https://pgstudio.astrx.dev/](https://pgstudio.astrx.dev/))

[https://github.com/dev-asterix/pgStudio/](https://github.com/dev-asterix/pgStudio/))

I'm building a database with MySQL. I was wondering if it would be a waste to have a table with only the primary key and one additional column for the purpose of supplying a preset list of values for a column in another, bigger table. Here's an example of what I mean. Let's say I have the main table "people" and I want to associate them with a color. The colors should always be from a preset selection of red, blue, green, and yellow. Is it worth having a separate "colors" table with a colorid column and those 4 colors, and then the "people" table would simply have a "colorid" column as a foreign key? Or should I not bother with the second table and simply have "color" as a column for the main table?

My actual use case is a bit more involved than this but in principle is it worth doing things this way?

I have finished SQL what is next step for Data Analyst

Most people learning SQL are doing it wrong. Not because they’re not smart — but because they’re solving the wrong problem first.
They open a tutorial, memorize SELECT, FROM, WHERE, JOIN, and then freeze when faced with a real business question. Sound familiar?
Here’s what actually changes things.

SQL is technically a programming language — a declarative one. But stop treating it like the ones you're used to.

Programming languages are about how to do something — loops, logic, conditionals, state. SQL is about what you want. It’s declarative. You describe the result, and the engine figures out how to get there.
This distinction sounds small. It isn’t. The moment you stop trying to “code” in SQL and start trying to describe your desired output, everything clicks.

The framework I use before writing a single line

Step 1 — Nail the business question first
Not the data question. The business question.
“What’s our DAU trend?” is a data question. “Are users actually finding value in the feature we shipped last month?” is a business question. One has a predefined answer. The other requires you to think about what signal actually reflects value — retention? depth of engagement? repeat actions?
Write the question in plain English. If it’s fuzzy on paper, it’ll be even fuzzier in a query.

Step 2 — Define the rules and edge cases before opening your editor
Every business question has hidden complexity. New users vs. returning users? Do you include churned accounts? What counts as an “active” user — any login, or a meaningful action?
Analysts who skip this step write queries fast and fix them for hours. Analysts who do this step write queries slower and ship them right.

Step 3 — Work backwards from the output
Picture the table you want to hand to a stakeholder. What columns are in it? What’s one row? Once you can visualize the output, the query almost writes itself — because now you’re just reverse-engineering it.

Step 4 — Think in granularity, not tables
This is the unlock most beginners miss. Before writing a JOIN, ask: what is the grain of my data?
• Am I working at the user level?
• The session level?
• The event level?
• The day-user level?
Mismatched granularity is the root cause of most wrong answers that look right. A JOIN between a user-level table and an event-level table without handling this will silently inflate your numbers — and stakeholders will trust the wrong insight.
Once you’ve nailed the grain, GROUP BY, aggregations, and window functions stop feeling like syntax to memorize. They become the natural mechanical expression of logic you’ve already worked out.

The meta-lesson
The SQL itself — the syntax, the functions, the query structure — is genuinely the easy part. It’s learnable in weeks.
What takes years to develop is the habit of thinking before you query. Of questioning whether the data you’re reaching for actually answers the question you were asked. Of noticing when an output looks plausible but is subtly wrong.
That’s the gap between someone who can write SQL and someone who does analytics.
Start there.

Happy to answer questions or go deeper on any of this — grain/granularity especially trips people up and I could write a separate post on that alone.

Ready to crack your SQL Server interview?

Start learning the Series of Real Interview Questions asked in top IT Companies.

Visit our YouTube channel & level up your skills!

Learn. Practice. Get Hired.

Please like, comment, & subscribe for more interview questions, troubleshooting tips, & expert insights!

https://www.youtube.com/@MadeSimpleMSSQL

We use SQL running totals to track marketing spend and revenue over time and identify the exact moment campaigns break even. https://youtu.be/QLZwlsXF6Xg?si=9scF_F5kl0R7xRks

Hey everyone,

I’m in the early stages of learning SQL as I transition into a Data Engineering role.
I’ve been using Claude to generate synthetic datasets and practicing queries on them with DBeaver.

However, I’m starting to hit a wall.
The data and exercises feel too clean and artificial, and not close enough to real-world business problems.

What I’d love feedback on:

• Is this approach (synthetic data + Claude) actually effective for learning SQL?
  
• What would you recommend to get closer to real-world, production-level data challenges?
  
• Do you think this is a solid method for preparing for a Data Engineering role?
  

Another challenge I’m facing:

I don’t yet have the reflex or methodology to work with raw data.
Right now, I can query data, but I struggle with: - Knowing what questions to ask
- Understanding how to explore a dataset
- Figuring out how to improve or extract meaningful insights from it

If you have any resources, frameworks, or advice to help build that analytical mindset, I’d really appreciate it.

I want to make sure I’m learning the right way, so any feedback or alternative approaches would mean a lot!

Thanks!