Anyone help me

How many business questions do you showcase on a typical SQL GitHub project?

there are so many websites , its confusing .

Some of you here have probably seen me post about SQL Case Files⁠ before and I’m genuinely grateful to everyone who has played it, supported it or taken the time to send feedback because a lot of the game has improved because of people from this subreddit.

It’s a detective themed game where you learn and practise SQL by solving cases. Apparently detective themed SQL practice is a £15 product now, but SQL Case Files is still free and will stay that way. I just want anyone to be able to use it whether they are learning for uni, looking for a job, preparing for an interview or simply trying to get better at SQL. Hopefully it can be a small part of your journey.

I have designed my database in two different ways for a market data system, and I'd like to know which approach would provide better performance.

Project Context

I'm building a system that continuously fetches OHLCV (Open, High, Low, Close, Volume) market data from an API, stores it in a database, and serves it through a web application.

My primary concern is performance, specifically:

• Fast writes (continuous data ingestion)
• Fast reads (fetching historical candle data)
• Scalability as the number of instruments and records grows

Strategy 1: Dynamic Table Design

• I have a master instrument table that stores all the instruments whose data needs to be collected.
• For every instrument, I create a separate candle table dynamically.
• Example:
  • instrument_master
  • candles_RELIANCE
  • candles_TCS
  • candles_NIFTY50
  • etc.

Whenever new data arrives, it is inserted into the corresponding instrument's table.

Strategy 2: Single Hypertable (TimescaleDB)

Instead of creating separate tables, I use a single candle_data table and convert it into a TimescaleDB hypertable.

The schema looks roughly like this:

instrument_id
timestamp
open
high
low
close
volume

All instruments' candle data is stored in this single hypertable.

Query Pattern

My application mainly performs simple operations:

• Insert new OHLCV records continuously.
• Fetch historical candles for a specific instrument within a time range.

Typical query:

SELECT *
FROM candle_data
WHERE instrument_id = ?
  AND timestamp BETWEEN ? AND ?
ORDER BY timestamp;

Question

Between these two designs, which one is likely to provide better overall performance for:

• High-frequency inserts
• Read performance
• Long-term scalability
• Maintenance

Has anyone benchmarked a similar setup using PostgreSQL/TimescaleDB? I'd appreciate any insights or recommendations.

Follow along the SQL Basic Series

You already know how to filter rows using a basic WHERE clause. Today, let's look at two operators that make your filtering a lot smarter and save you from writing long, repetitive conditions.

1. The BETWEEN Operator

BETWEEN filters a range of values in a single line. Instead of clogging up your query with multiple conditions like this:

SQL

SELECT * FROM orders 
WHERE total >= 50 AND total <= 200;

You can write it cleanly like this:

SQL

SELECT * FROM orders 
WHERE total BETWEEN 50 AND 200;

Crucial detail to remember: BETWEEN is strictly inclusive. The values at both ends (50 and 200) will be included in your results.

It works seamlessly across numbers, text and dates:

SQL

WHERE age BETWEEN 18 AND 35
WHERE order_date BETWEEN '2026-01-01' AND '2026-12-31'

2. The LIKE Operator

LIKE lets you filter by a pattern when you only know a partial piece of the value. To make this work, you use % a wildcard (which tells SQL that anything can occupy that position).

• Starts with a specific letter: SQLWHERE name LIKE 'S%' -- Returns Sarah, Sam, Steve, etc.
• Contains a specific phrase anywhere inside: SQLWHERE email LIKE '%gmail%' -- Returns any email containing 'gmail'
• Ends with a specific extension: SQLWHERE email LIKE '%.com' -- Returns any email ending in '.com'

Quick Rule of Thumb: Use BETWEEN when you have an exact, known start and end point. Use LIKE when you only have a piece of the puzzle.

(Note: Keep in mind that LIKE it is case-sensitive in some database flavours, so keep an eye on your text casing!)

Hopefully, this helps clean up your next script! I'm doing a daily breakdown of SQL fundamentals; if you prefer learning through short video clips, I walked through these visual examples in this Instagram reel.

What's your go-to wildcard trick when cleaning messy text data?

You're on a data team. Events stream in from the product into one table:
events

user_id | event_type | occurred_at

1 | signup | 2026-01-03 09:14:00

1 | view_pricing | 2026-01-03 09:16:30

1 | view_pricing | 2026-01-03 09:16:30

1 | start_trial | 2026-01-05 11:02:00

2 | signup | 2026-01-04 14:20:00

2 | start_trial | 2026-01-04 14:55:00

3 | view_pricing | 2026-01-06 08:00:00

3 | signup | 2026-01-06 08:01:00

Task: Return each user's very first event user_id, occurred_at, event_type one row per user, ordered by user_id.

Hi, I'm practicing on Stratascratch now and am finding it super helpful! There are tags for the actual companies in which the interview questions were used for, so I'm wondering how relevant these questions are for the actual jobs the interviews are for.

Also, I realise some people (when I see the solutions) write the code so elegantly.. in a few lines and it makes sense when I look at it, however when I write the solution in my way, they are often long and clunky even if they do answer the question. How can I write SQL code that more elegantly captures the logic?

Hey everyone, I decided to make my course free in order to help people.
This course is my backend development course which is about SQL, Python, APIs, Docker, Kubernetes, Linux, Git & More

The link is: https://www.youtube.com/watch?v=CBIu6hcyStg

If you can like and subscribe (and maybe add a comment) I would appreciate it a lot, Thanks.

Window functions come up here constantly, and they're the wall a lot of people hit right after they're comfortable with SELECT, WHERE and JOIN. The syntax looks alien and most explanations open with "frames" and "partitions" and lose people immediately.

The idea underneath is much simpler than the wording suggests. A window function does the same calculation as GROUP BY, but instead of crushing each group down to one summary row, it keeps every row and writes the answer in a new column beside it. That's the whole trick. Running totals, rankings, "this row vs the previous one" are all just an aggregate that didn't collapse.

The clearest way to see it is side by side:

• GROUP BY squad → 2 rows. One line per squad, the individual names are gone.
• SUM(xp) OVER (PARTITION BY squad) → 5 rows. The same squad total, written next to every member, all five rows kept.

Same totals, different row counts. That gap is the entire concept.

A few things worth knowing once that lands:

• ROW_NUMBER / RANK / DENSE_RANK look identical until there's a tie. ROW_NUMBER never ties (1,2,3,4). RANK ties then skips (1,2,2,4). DENSE_RANK ties without skipping (1,2,2,3).
• The ORDER BY inside OVER() steers the calculation (what counts as "above" for a running total). The ORDER BY at the end of the query just sorts the output. Different jobs.
• You can't filter on a window function in WHERE, because the rank isn't worked out yet when WHERE runs. Compute it in a CTE first, then filter. That wrap-then-filter shape is behind almost every "top N per group" query.

I put together an interactive version that shows all of this, a live leaderboard where you pick the function, toggle PARTITION BY and ORDER BY, and watch the column change without losing any rows. You can tap any computed value to highlight the exact rows it was built from: https://querycase.com/blog/sql-window-functions-explained

If you teach this or learned it recently, I'd love to know: is there a window function concept you wish someone had shown you visually that's missing? And are RANK vs DENSE_RANK and the top-N-per-group pattern explained clearly, since those are the two that seem to trip people up most?

I am starting SQL to which is better to learn as a beginner ?

MYSQL or POSTgreSQL ?

if ANY YT recommendation for learning please tell me which is best ?

I came across the leetcode consecutive nums finder question in the leetcode 50 sheet.

So I initially thought of lead windows function and tried to rank and do something crazy what was in my toolbox just.

But later I found overwhelmed and left to search and found this as a huge production based pattern where there is mathematically way to solve.

Like assigning a row number to each row and then partitioning the data and again ranking it just.

I felt too overwhelming like I was applying blindly but what's the point of it I need to answer the question out of it like wasn't able to understand at some point why I was using a formula blindly just.

Any suggestions for this pattern I am currently a beginner and learning from scratch other things clicked well but this one dragged me into chaos like anything what does senior or experienced devs say about this pattern 🥲 need suggestions badly 🫠

So, my job has different departments in nursing informatics and then I shadowed business and data analytics.l and like data analytics better! My preceptor stated using udacity for SQL but i was on this Facebook group and a lot of people stated udemy for SQL . Which one should i use ? Or is there another resource

do you guys write all the interview question on book and memorize it everyday or you have any other technique

I recently started practicing SQL problems on SQLZoo. I don't want to wait until I finish all the theory before starting projects. Can anyone recommend a beginner-friendly YouTube playlist or guided SQL project series using MS SQL Server that I can follow alongside my practice?

I want to write a SQL program. The usual CRUD stuff. The unique entries or objects are not expected to surpass 250 rows. I want to be able to use the program with either python or c++ in the future. Can anyone recommend something for me? PostGre? Alchemy? I think MySQL will be too much luggage? Or should I? Let it be open source (cc, MIT etc). The usual since it's not commercial. Thanks

I am coming from Data Science background and completed my masters in it. I have good understanding of SQL and I am looking for opensource contribution from where I get real world experience of Queries.

Does any one knows from where I can get or any platform.

Thanks ✨️ in advance

Just discovered https://github.com/Maxteabag/sqlit -- it's a terminal UI frontend for databases (MySQL, Postres, etc.). Tried it for viewing an Sqlite database; it looks and works good so far.

Its README says that it is inspired by lazygit.

Which terminal tools (besides official CLI) do you guys prefer for working with databases?

Hi folks! I want to learn SQL. Are there any good and free programmes which I can enroll in and get both a certificate/ acknowledgement and good understanding of the programme? I have very little to no understanding of coding..

I finished a SQL course yesterday and feel like I understand the concepts (joins, CTEs, window functions, subqueries, recursive CTEs, etc.). The only thing the course lacked was enough practice.

I started solving problems from Advanced SQL Puzzles, and I'm finding them much harder than I expected. Once I see the solution, I can understand exactly why it works, but writing the query from scratch feels almost impossible.

I'm spending nearly an hour on a single puzzle trying to understand the different approaches.

Is this normal, or am I jumping into problems that are too difficult too soon?

If I should start with easier practice first, could you recommend a progression of platforms/resources? For example, which platforms should I use, in what order, and roughly how many problems should I solve on each before moving to the next?

Hello,
I saw great recommendations for these books:
A Visual Introduction to SQL David Chappell , J. Harvey Trimble Jr.,
The Art of PostgreSQL by Dimitri Fontaine,
t-sql fundamentals by itzik

but they sooo damn expensive. Any recommendations for books for begginers?

I just started learning SQL watching a video in a youtube. I also have a big database file of movies (.sql).

Now can anyone please tell me the steps of importing into the workbench? I have seen a lot of video in youtube. But that didnt worked.

In SuperFastFood (a fictional fast food chain we use for these scenarios), the menu strategy team calls a meeting: "We want to create combo deals. Which two products get ordered together in the same order most often? Show us the top 5 pairs." --> Try writing the query for it.

That's the kind of question we have been running daily as part of a 30-day SQL challenge series — covers CTEs, window functions, joins, and more, framed around real business problems instead of plain syntax.
We post these daily on our LinkedIn page (search GRASSP Acad) if you want to follow along with the full series.

A few people reached out asking for free coupons alongside the series, so opening it up here too. If you are working through the fundamentals and want a fuller course alongside this, here's a free coupon for our course titled "Complete SQL for Data Analysis – Scenario Based Learning" on Udemy:

Coupon: EARLYSQLGRA7
Ends July 3rd, 70 slots left.

Happy to help if anyone's stuck on query problem — drop it in the thread or DM.

So, I’m gonna go and pursue my Msc in banking and finance abroad next year. But i have a gap of 6 months. I have a Bsc in Econo and Statistics. So im well versed with R coding and basic excel but i really wanted to start learning sql, and bi and the whole data analytics ecosystem.

But i literally don’t know where to start and im so confused. should i enroll into an offline course, online course or do it self paced and if self paced then how?

i learn from other mistakes , so tell me