KajoData blog

Data, work and everything around them.

I write about data analysis, useful tools and changing careers. Expect examples you can check and ideas you can put to work.

Articles: 170

Career & business

9 interview questions: how to prepare your answers

I work through nine questions worth preparing your own examples for. Learn to explain decisions, limitations and results without pretending to know an interviewer's hidden intentions.

Updated 11 Nov 202613 min read

Career & business

Changing careers into data analytics: four elements of a plan

I turn four elements of a career change into practical decisions for an ordinary week. Includes a sample learning plan, project completion criteria and a way to restart after a break.

Updated 11 Nov 202612 min read

Career & business

Active listening: five mistakes in a tech job interview

I explain five communication mistakes in tech interviews and practical ways to address them. Includes clarifying questions, focused answers and an honest response when you lack technical knowledge.

Updated 11 Nov 202613 min read

Excel

Excel errors: find the cause and repair the formula

I trace errors back to inputs and references, explain small examples and separate repairing a cause from choosing a readable fallback.

Updated 10 Nov 202611 min read

SQL

How to learn SQL: a plan from SELECT to independent analysis

I organise SQL learning around questions and checks, including row meaning, missing values and the number of matches after a join.

Updated 10 Nov 202611 min read

Excel

How to learn Excel: from a table to a reliable report

I explain what to learn next and how to recognise progress, using a small report you can check, refresh and hand over.

Updated 10 Nov 202611 min read

Excel

PivotTables in Excel: from sales lines to a useful report

I build a report from four sales lines, explaining field areas, control totals and why a row count can differ from an order count.

Updated 9 Nov 202612 min read

Excel

XLOOKUP in Excel: matching, missing codes and search direction

I use a small catalog to explain all six arguments, range alignment and the difference between the last match and the latest record.

Updated 9 Nov 202610 min read

Excel

VLOOKUP in Excel: price lists, keys and matching

I follow a product code to its price and explain when FALSE matters, how references move, and why the first match can be insufficient.

Updated 9 Nov 202612 min read

Excel

Rank without ties in Excel: use row order to break a tie

I work through five scores and show why equal points receive separate ranks. The tie breaker is row order, so the rule stays visible.

Updated 8 Nov 20267 min read

Excel

Weighted average in Excel: values, weights and group means

I work through grades, customer groups and unit prices, showing how the choice of weights changes the question your average answers.

Updated 8 Nov 20269 min read

Excel

Find workbook links in Excel: formulas, names and charts

I trace external workbook dependencies from the links pane to the cells and objects using them, then explain how to choose a repair.

Updated 8 Nov 20266 min read

SQL

EDA in SQL: understand the data before reporting a result

Follow six orders, identify missing values and repeated records, and establish the conditions for a trustworthy reporting result.

Updated 7 Nov 202612 min read

python en

Python charts with Matplotlib: lines, points and histograms

Match the chart to the question, trace histogram counts and export a figure with readable labels and units.

Updated 7 Nov 202612 min read

python en

Text to a Python list: lines, words and empty fields

Choose lines or words as list items, preserve meaningful whitespace and recognise when a CSV reader is the right tool.

Updated 7 Nov 20266 min read

Career & business

How to improve a weak CV with relevant evidence

I explain how to distinguish missing experience from an unclear description and show your contribution without invented results or universal ATS promises.

Updated 6 Nov 202614 min read

Career & business

Career change after thirty: preparing a move into data analysis

I show how to connect earlier work to a new direction, test your interest in analysis and prepare a transition around realistic time constraints.

Updated 6 Nov 202614 min read

Career & business

When staying with a company helps your career

I explain how to distinguish development in a familiar workplace from staying through habit, and how to investigate your options before deciding to move.

Updated 6 Nov 202614 min read

Career & business

AI in a team: why I look at tasks before job titles

Why technical understanding matters in my view of AI at work, and how I distinguish useful coordination from passing tasks between people.

Updated 5 Nov 20269 min read

Career & business

Cynicism at work: when a joke replaces your next career step

My perspective on the workplace joker, quiet determination and turning frustration after an unsuccessful attempt into one practical improvement.

Updated 5 Nov 20268 min read

Excel

AND and OR in Excel: conditions, intervals and IF

I use one table to show who meets every requirement and who meets at least one, then explain intervals and grouped rules.

Updated 5 Nov 20267 min read

Excel

IF in Excel: thresholds, outcomes and missing data

I walk through a decision for one row, including the difference between > and >= and between a missing result and a measured zero.

Updated 5 Nov 20267 min read

Excel

SUMIFS in Excel: product, region and reporting month

I show which transactions produce a total of 150 and why the others are excluded. Build a report with product, region, date and status criteria.

Updated 5 Nov 202611 min read

SQL

MySQL ROWS UNBOUNDED PRECEDING: running totals and window frames

I turn six events into running totals and explain why events sharing a date require an explicit decision about order and reporting detail.

Updated 4 Nov 202613 min read

SQL

Star schema or snowflake schema: designing a sales model

I model the same three sales lines in both layouts, separate data detail from dimension normalization and explain what to check before choosing.

Updated 4 Nov 202613 min read

SQL

SQL SELECT DISTINCT: unique values, combinations and traps

I explain why the country list has four rows, its count is three and adding a city changes the answer. You will also learn when DISTINCT hides a mistake.

Updated 4 Nov 202613 min read

SQL

SQL subqueries: scalar values, IN, EXISTS and derived tables

I explain the result shape each subquery must provide, the NULL trap in NOT IN and why logical dependencies do not specify an execution plan.

Updated 3 Nov 202612 min read

SQL

SQL INNER JOIN: matches, keys and duplicate rows

I trace each matching pair, explain why records disappear or multiply and show how composite keys and EXISTS change the result.

Updated 3 Nov 202612 min read

SQL

SQL LEFT JOIN: unmatched rows, counts and totals

I show why three customers produce four rows, how unmatched customers remain visible and why order counts need a non-null key.

Updated 3 Nov 202612 min read

Career & business

AI at work: context, control and your own analytical skills

How I organise knowledge and tasks for AI while keeping the skills and understanding I need to take responsibility for the result.

Updated 2 Nov 20269 min read

SQL

UNION ALL, UNION and INTERSECT: what are you combining?

I compare two customer lists to explain repetitions, common rows and NULL, then show why adding a selected column changes the result.

Updated 2 Nov 202612 min read

SQL

WHERE in SQL: filters, NULL and date boundaries

I filter six orders to select an October population, showing how parentheses, missing statuses and month boundaries change the result.

Updated 2 Nov 202612 min read

SQL

SELECT in SQL: columns, calculations and readable output

I use four orders to explain column selection and calculated amounts, then show how aliases, duplicates and sorting affect the result.

Updated 2 Nov 202614 min read

statistics

How to calculate the median and interpret it alongside the mean

Calculate the median step by step, compare it with the mean, and understand ties, missing values, aggregation levels and the limits of a single summary.

Updated 1 Nov 202612 min read

SQL

SQL clause order: from source rows to the final result

Follow six orders through filtering, grouping and a limit. I explain aliases, ties, join cardinality and why logical order differs from the database plan.

Updated 1 Nov 202612 min read

Excel

Translate Excel formulas between English and Polish

A bilingual function glossary and complete formula examples covering separators, decimals, criteria, date format codes and version compatibility.

Updated 1 Nov 202611 min read

Career & business

Data cleaning: improve data without deleting its meaning

I follow a raw table through cleaning and show when to remove a record, preserve a missing value or investigate an unusual amount before publishing a report.

Updated 31 Oct 202612 min read

Career & business

How much math does a data analyst need? Start with these foundations

My route from Polish studies to data did not require waiting for another degree. It did require learning to explain calculations that software cannot interpret for me.

Updated 31 Oct 202612 min read

tableau en

Tableau data blending: compare sales and targets without inflated totals

I use a small sales example to explain why a join can inflate targets, how blending combines aggregates, and when relationships offer a better model.

Updated 31 Oct 202612 min read

Excel

Dollar signs in Excel: relative, absolute and mixed references

I explain which parts of a reference should move when a formula is copied. Practice one shared parameter and a small two dimensional scenario table.

Updated 30 Oct 202612 min read

tableau en

MoM and YoY in Tableau: percentage change with the right base

I explain MoM and YoY formulas by tracing their comparison values. Learn why missing months, zero bases and date filters can change the meaning of a result.

Updated 29 Oct 202613 min read

tableau en

What is Tableau? From a table to a useful dashboard

I walk through a small sales analysis and explain the tools around it. Learn what Tableau does, where the analyst makes decisions, and how to check a first dashboard.

Updated 29 Oct 202612 min read

Excel

Python in Excel: cloud calculations and a maintainable workflow

Understand where Python runs, how inputs reach it and what a recipient needs from the output. Build a small, understandable analysis before expanding the workbook.

Updated 28 Oct 202611 min read

Excel

SUBSTITUTE in Excel: occurrences and safe text replacement

Replace every matching fragment or just one occurrence. Distinguish SUBSTITUTE from REPLACE and recognize when a cleanup rule changes the meaning of your data.

Updated 28 Oct 20266 min read

Excel

HLOOKUP in Excel: product codes and thresholds

Retrieve a price below a product code and a rate from an ordered threshold table. Understand why HLOOKUP's last argument changes what the result means.

Updated 28 Oct 20266 min read

SQL

SQL WHERE and GROUP BY: turn rows into a useful report

Follow six orders through WHERE, GROUP BY and HAVING. See how NULL changes counts and averages, and how to check what a grouped result actually means.

Updated 27 Oct 202611 min read

Tableau

Tableau dual axis: two measures and an honest scale

Build a dual-axis view, separate units from numeric scale, and decide when Synchronize Axis produces a meaningful comparison.

Updated 27 Oct 202611 min read

Excel

Excel DATE: build dates and catch input mistakes

Combine year, month and day, understand overflowing date parts, and separate a valid calculation from a trustworthy date in your source data.

Updated 27 Oct 202611 min read

Excel

Excel tables: organise records, formulas and filtered totals

I build an understandable source table, from defining one record to calculated columns, filtered totals and checking newly added rows.

Updated 26 Oct 202613 min read

Excel

Import CSV into Excel: delimiters, encoding and column types

I show how to read a CSV deliberately, preserve identifiers and verify the result before saving a repeatable import.

Updated 26 Oct 202612 min read

statistics

Percentage change: growth, decline, MoM and YoY

I explain the formula through small examples, then check which comparisons are meaningful and how to describe the result clearly.

Updated 26 Oct 202613 min read

Career & business

Lost motivation to learn? Return to one concrete task

I suggest a way to repair a study plan after a break: identify the obstacle, choose a small task, check the result and decide what comes next. Constant enthusiasm is not a requirement.

Updated 25 Oct 202613 min read

python en

SQL or Python: which should a data analyst learn first?

I start with where the data lives and the result I need. Using the same orders, I demonstrate SQL, Python and their cooperation before suggesting a learning sequence.

Updated 25 Oct 202613 min read

Career & business

Data analyst or programmer? Choose through practical work

I explain how to explore both careers when you already have a job and limited study time. Two practical trials help you choose a direction without guessing your future salary.

Updated 25 Oct 202614 min read

python en

Counting list elements in Python: dict, Counter and hashing

I turn a list into a frequency table and check what the numbers represent, including missing categories, ties and the surprising equality of True and 1.

Updated 24 Oct 202612 min read

python en

Python lists: indexing, slicing and shallow-copy traps

I trace list operations through concrete positions and results, including the difference between a new outer list and independent nested data.

Updated 24 Oct 202612 min read

python en

Reading files in Python: text, CSV and import checks

I build a complete file-reading example and check paths, Unicode, empty fields and zeros before calculating a result.

Updated 24 Oct 202612 min read

SQL

SQL CTEs: WITH and a monthly report step by step

I name calculation stages and build a report that retains empty months. Learn CTE scope, aggregation, missing values and how to check each result.

Updated 23 Oct 202612 min read

SQL

SQL formatting: readable code and verified results

I separate SQL style preferences from calculation changes. Use a small dataset to check aliases, joins, filters and safe refactoring.

Updated 23 Oct 202612 min read

SQL

SQL SELECT: columns, filters and predictable results

Start with SELECT * and build a result you can verify. I explain column selection, filters, missing values and resolving ties before applying LIMIT.

Updated 23 Oct 202613 min read

Career & business

How to plan a data analysis project: question, scope and acceptance

I show how to turn an analysis idea into a project you can finish: define the question, inspect the data, limit the scope and deliver an answer someone can use.

Updated 22 Oct 202613 min read

Career & business

IT conferences for introverts: preparation, conversations and a calmer plan

I organise conference attendance around a useful question, a few meaningful conversations and one idea to test afterwards. You do not need to meet the entire room.

Updated 22 Oct 202613 min read

Career & business

How to receive feedback: from a difficult comment to a specific change

I separate difficult feedback into facts, interpretations and a next step. Here is how to ask for specifics, disagree constructively and evaluate an improvement.

Updated 22 Oct 202613 min read

Career & business

Data analysts and AI in 2026: fundamentals for checking results

I show what to delegate to AI, which decisions need explicit ownership and how to detect working code that produces a wrong answer. We walk through a small SQL example and a way to deliver verified analysis.

Updated 21 Oct 202612 min read

Career & business

Data analyst collaboration: 6 behaviours that make work harder

I look at observable behaviour rather than labels: what blocks a team, how to discuss it and how to check improvement. With examples of feedback, knowledge transfer and reviewing your own habits.

Updated 21 Oct 202613 min read

Career & business

5 junior data analyst mistakes and work habits that help

I walk through five habits to improve in your first analyst role, from agreeing on a report's purpose to discussing your development. With examples of a brief, a blocker update and a handover, without promises of job security.

Updated 21 Oct 202613 min read

Career & business

Data analyst career paths: management, data science or business?

I use one delivery problem to compare the work of a manager, a data scientist and a business specialist. Then I show how to plan a small trial of your chosen direction.

Updated 20 Oct 202613 min read

Career & business

Grow in your team: make your work visible and help others

I explain how to choose useful work, communicate progress and help colleagues without taking over their entire queue. You will also get an example of a contribution record and a way to discuss your next responsibilities.

Updated 20 Oct 202613 min read

Career & business

Your first data analyst job: technical skills and collaboration

I walk through one small analysis, from a vague request to a checked answer. Learn how to agree on definitions, ask for useful feedback and show your contribution in a portfolio.

Updated 20 Oct 202614 min read

Career & business

What a Data Analyst Needs to Know: 10 Skills You Can Test on a Project

A list of tools tells me little about what you can deliver. I use one small project to show how to test ten analyst skills, from clarifying a question to explaining a recommendation.

Updated 19 Oct 202616 min read

Career & business

Data analyst career map: roles, responsibilities and your next step

I explain six areas of data work and the evidence that can show readiness for each. Build your own career map around real responsibilities and a small practical project.

Updated 19 Oct 202614 min read

Career & business

Data analyst technical interviews: an answer, an example, a limitation

Knowing a definition is a starting point. I show how to explain a technical answer, predict a small example's result and identify the limitation that matters.

Updated 19 Oct 202613 min read

Career & business

Financial KPIs: COGS, contribution margin, OPEX and cash

Positive profit can coexist with falling cash. Follow one cost, margin and payment model with reproducible calculations and explicit assumptions.

Updated 18 Oct 202613 min read

Career & business

Logistics KPIs: time, timeliness, returns and cost

One order queue shows how to measure time, fulfilment and cost without hiding delays. Separate orders, parcels, product units and available inventory.

Updated 18 Oct 202613 min read

Career & business

Ecommerce KPIs: CAC, AOV, retention, LTV and payback

One shop, six orders and consistent definitions. Learn to calculate ecommerce KPIs and distinguish sales, contribution after costs and predicted customer value.

Updated 18 Oct 202613 min read

Career & business

How to learn data analysis effectively: five principles

Move from completed lessons to skills you can demonstrate. Practise, revisit and assess progress through concrete tasks, without promises of a quick promotion.

Updated 18 Oct 202613 min read

Career & business

Data analysis methods: from business question to decision

Conversion falls while group rates stay unchanged. A shop example shows how to choose an analytical method and establish what remains unknown.

Updated 18 Oct 202613 min read

Career & business

Data problems in companies: definitions, collaboration and ownership

Three reports show different order counts. I use one example to explain how to investigate the difference, agree on a definition and decide who will fix it.

Updated 18 Oct 202614 min read

Career & business

Power BI skills for analysts: five areas to practise

Build a report you can explain and check. Explore five Power BI skill areas with a tiny exercise covering filters, shares and missing amounts.

Updated 18 Oct 202613 min read

Career & business

How to analyse your own data: a first small project

I work through a small reading diary, from defining a row to calculating averages, evaluating a target and explaining missing observations.

Updated 18 Oct 202612 min read

Career & business

Tableau or Power BI? How to choose as a beginner

Start with your goal and audience. Understand free editions, local work and publication, then compare the tools through one consistent exercise.

Updated 18 Oct 202613 min read

Career & business

5 statistical mistakes analysts make: check the conclusion

I show how correct figures can support an incorrect story, and how to check denominators, samples, distributions and the scope of a recommendation.

Updated 18 Oct 202611 min read

Career & business

Analytics Engineer: data models, tests and maintenance

A shared table needs ownership, definitions and checks. Explore analytics engineering through an order model and the changes its team must maintain.

Updated 18 Oct 202613 min read

Career & business

SQL for data analysts: from question to verified result

A query can run successfully and still answer the wrong question. Work through order grain, joins, missing amounts and a reproducible reconciliation.

Updated 18 Oct 202613 min read

Career & business

Meetings and time for analysis: plan a workable week

A calendar needs room to carry out decisions. Explore a weekly plan covering analysis, meetings, communication, breaks and unexpected work.

Updated 18 Oct 202613 min read

Career & business

Outlook, Slack and Teams notifications: choose useful signals

Calmer work starts with useful signals and clear team expectations. Explore application settings and a practical way to verify urgent exceptions.

Updated 18 Oct 202613 min read

Career & business

Animation engineering: a conversation with Adrianna Bielak

How does code make movement respond to a player? I revisit my conversation with Adrianna Bielak and explain the technical ideas through simple examples.

Updated 17 Oct 20269 min read

Career & business

15 KPIs I want every data analyst to understand

Acquisition gets cheaper, sales go up, and somehow the money does not follow. Here is how I connect 15 business metrics and check the story behind the cheerful green arrows.

Updated 17 Oct 202616 min read

Career & business

Data Analyst vs Business Analyst vs BI Developer: roles in a project

I use one project to distinguish clarifying a need, investigating data and building a reporting solution that remains useful after delivery.

Updated 17 Oct 202612 min read

Career & business

How Power Query works: from a raw file to a repeatable process

Power Query remembers how to prepare data. I explain what it repeats, how to verify the result and why a new source file can still require a change to the rules.

Updated 17 Oct 202612 min read

Career & business

Can a humanities graduate become a data analyst? My route from literature

I studied Polish literature. Before analysing data professionally, I was trying to understand where my money went. Here is that journey, the skills I could bring with me and the technical work I still had to learn.

Updated 17 Oct 202613 min read

GPT-5 vs Gemini 2.5: what my analysis test showed

I revisit four tasks used to compare GPT-5 and Gemini 2.5, explain what the results support and show how I would check a model's analytical work.

Updated 17 Oct 202613 min read

Career & business

5 reasons Excel still belongs in an analyst's toolkit

I use one small example to show where Excel helps, what to check after a refresh and how to deliver a workbook someone else can understand.

Updated 17 Oct 202613 min read

Career & business

Why I enjoy being a data analyst: four reasons and one example

I enjoy the moment when numbers begin to explain a specific problem. I work through a question about late deliveries to show what makes analytical work satisfying to me.

Updated 17 Oct 202613 min read

Career & business

Beginner data analyst mistakes: how to recognise and correct them

Knowing a tool can feel like independent analysis. I show how to check your foundations, limit a project and explain a result whose limitations you understand.

Updated 17 Oct 202613 min read

Career & business

Data analyst or programmer? Try the work before choosing the title

Before choosing a career from a list of technologies, try solving a small problem in two different ways. I compare the work, the responsibility and what you can learn from each experiment.

Updated 17 Oct 202613 min read

Career & business

Data Analyst vs Data Scientist: tasks, responsibility and choosing a path

I use one delivery scenario to show how the question, output and checks change between analysis and predictive modelling.

Updated 17 Oct 202612 min read

Career & business

Data analyst disadvantages: how to evaluate a role and its daily work

I explore the less comfortable parts of analysis and the questions that help you understand how a particular team actually works.

Updated 17 Oct 202612 min read

SQL

A histogram in SQL: from orders to a customer distribution

The average customer places a few orders. But how many buy once, and how many return regularly? I build the distribution step by step, including the mistakes that make valid SQL answer the wrong question.

Updated 17 Oct 202614 min read

SQL

SQL pivot tables: CASE WHEN, COUNT and the traps around NULL

A pivot can look correct while losing orders. I show how to count categories, distinguish zero from missing data and reconcile the columns with the source.

Updated 17 Oct 202612 min read

Career & business

Data cleaning: five steps that preserve the meaning of your analysis

Removing duplicates takes a click. Deciding what counts as a duplicate takes thought. I explain five stages of data cleaning and how to check that the tidy result still answers the original question.

Updated 17 Oct 202613 min read

Career & business

LinkedIn for an analyst job search: profile, projects and routine

I show how to connect a clear profile, useful conversations and vacancy reviews into a process you can assess beyond view counts.

Updated 17 Oct 202612 min read

Career & business

Data analyst CV mistakes: show your skills and experience clearly

I show how to replace general claims with accurate descriptions of work that a reader can understand and discuss in an interview.

Updated 17 Oct 202612 min read

Python

Python variables, data types and operators: a practical starting point

Two names can share one list, and the text False can behave like true. I explain Python basics through a small data task, including the quiet mistakes that change your results.

Updated 17 Oct 202613 min read

Excel

VLOOKUP, HLOOKUP and XLOOKUP: one practical Excel example

A formula can return a number and still point to the wrong product. I walk through a small product lookup, then deliberately break the data to show what needs checking.

Updated 17 Oct 202613 min read

SQL

Advanced SQL queries: CTEs, windows and rankings in one example

A query with three CTEs can look impressive while calculating the wrong sales total. I build one analysis step by step, keeping track of row meaning, missing values and the order of calculations.

Updated 17 Oct 202612 min read

python en

Python basics: from a variable to a checked pandas report

I follow one complete example from reading orders to checking inputs and explaining a grouped report without hiding missing amounts.

Updated 17 Oct 202612 min read

SQL

SQL basics: from your first table to a result you can explain

A query can run successfully and answer the wrong question. I work through six orders to show how selection, grouping, missing values and result checks fit together.

Updated 17 Oct 202612 min read

Excel

Advanced Excel formulas: calculations, lookups and error checks

A useful formula produces a result you can explain and verify. I use six records to connect calculations, lookups and text processing in a readable worksheet.

Updated 17 Oct 202613 min read

Career & business

Difficult interview questions: prepare answers you can explain

I show how to turn real experiences into clear answers that hold up when the interviewer asks what you did and how you checked the result.

Updated 17 Oct 202613 min read

Career & business

Data analysis for introverts: focused work and clear communication

You can prefer quiet work and still collaborate well. I look at the conversations involved in data analysis and how to give them a useful structure instead of constantly improvising.

Updated 17 Oct 202615 min read

Career & business

Why can’t I find a job? How I approach a career change into analytics

Another course finished, another CV sent, still no reply. I break a career change into decisions you can act on: the role you target, the experience you build and the evidence you show.

Updated 17 Oct 202615 min read

AI in everyday life: what I use it for and what I check

AI can save me a lot of clicking. It can also produce a very fluent explanation of something completely wrong. Here is how I choose tasks, give useful instructions and check the result before celebrating the time I saved.

Updated 17 Oct 202614 min read

Career & business

Designing a data dashboard that helps someone make a decision

An attractive dashboard can still suggest the wrong conclusion. I use delivery data to connect the reader's question, correct measures and a clear layout with a practical usability test.

Updated 17 Oct 202612 min read

Career & business

How to become a data analyst: learning, a project and your first applications

I explain how to connect tools through one project, document your skills and prepare to discuss the work of a data analyst.

Updated 17 Oct 202612 min read

Career & business

Who can work as a data analyst? Four traits you can practise

I show how to explore your fit for data analysis through observable behaviour, a worked example and useful feedback.

Updated 17 Oct 202613 min read

Excel

Array formulas in Excel: from one cell to a complete list

One formula can calculate six values, select matching rows or create a list of categories. I explain how to predict its output and catch mistakes before they reach a report.

Updated 17 Oct 202613 min read

statistics

Z-scores and standard deviations: calculation and interpretation

I explain distance from the mean, show how to check the calculation and identify what a z-score cannot establish about rarity.

Updated 17 Oct 202613 min read

SQL

SQL JOIN types: how I combine tables and check the result

Two tables, one JOIN and suddenly revenue doubles. Unfortunately, only in the report. Here is how I choose a join for the question and check that the result still represents the right things.

Updated 17 Oct 202614 min read

Career & business

Why I Really Became a Data Analyst: On Cigarettes, Shakespeare, and the Art of System Building

Discover the true story of how a Polish literature graduate went from tracking cigarettes in Excel to becoming a Data Architect earning 25k PLN.

Updated 3 Aug 202613 min read

Career & business

Will AI Replace Data Analysts and Consultants? On Artifact Reduction, "AI Slop", and the True Human Value in Data

Will AI make data analysts and consultants obsolete? Discover why generating slides or code isn't enough and where true human analytical value lies.

Updated 29 Jul 202612 min read

Career & business

Do I Regret Leaving My Full-Time Job? On Courage, Fear, and Forging Your Own Path

Wondering if you should quit your job? Read my story of transitioning from a Data Architect to a business owner. Fear, courage, and tough IT career choices.

Updated 27 Jul 202613 min read

Career & business

I Lie, Therefore I Work? What an Ex-Google Recruiter Says About Job Interviews (And Why She's Right)

Is honesty always the best policy in a job interview? I analyze advice from a former Google recruiter to help you strategically land a job in tech and data.

Updated 24 Jul 202610 min read

Career & business

7 Levels of Job Hunting in Data Analytics and Tech: Where Are You and How to Stop Wasting Time?

Applying for jobs with zero response? Discover the 7 levels of job hunting in data analytics and IT. Identify your mistakes and speed up your hiring process.

Updated 8 Jul 202612 min read

Career & business

6 Unconventional Career Tips for Data Analysts: The Brutal Truth About Corporate Promotions

Discover 6 politically incorrect tips to fast-track your career in data analytics. Learn how to strategically use Excel, SQL, and psychology to win in the corporate world.

Updated 6 Jul 202611 min read

Career & business

From Imposter Syndrome to Artificial Intelligence: The Real Face of a Data Analyst's Career

Discover the unvarnished truth about working as a data analyst. Kajo Rudziński breaks down the myths surrounding English requirements, imposter syndrome, and AI.

Updated 6 Jul 202618 min read

Career & business

A New Era in Technology and Data

Wondering what an AI Engineer is and if it's worth the pivot? Discover the career path, salary expectations, and necessary tools for this innovative IT role.

Updated 24 Jun 202613 min read

Career & business

What is AI Really Stealing From Us? The Hidden Cost of Automation

Is artificial intelligence destroying our critical thinking and writing skills? Discover how to maintain your human competitive edge in the tech market.

Updated 21 May 202610 min read

Career & business

Behind the Scenes of IT: What the Tech Hype Won't Tell You. A Conversation with Natalia Kierczuk

Discover the brutal reality of working as a business analyst in IT. Natalia Kierczuk (IT bez kodu) reveals industry myths, AI's impact, and corporate secrets.

Updated 20 May 202629 min read

Career & business

English in IT: How to Stop Being Afraid and Start Promoting Yourself? A Conversation with Wiktoria Sitko

Discover why a B2 level isn't enough in IT and how to effectively learn English to accelerate your career. Interview with Wiktoria Sitko on language blocks and learning.

Updated 14 May 202611 min read

Career & business

Fear of Being Fired? Don't Just Wait—Take Control of Your Career

Afraid of losing your job? Learn how to build a financial runway, develop new skills, and create a strategy to turn a crisis into a career success.

Updated 13 May 20269 min read

Career & business

Every Stage of Career Change: A Psychological Roadmap for Switching Professions

Discover the real stages of a career change. Learn the psychological roadmap of switching professions – from the first spark of interest to success in a new industry.

Updated 11 May 20267 min read

Career & business

What’s the Point of It All? On Ambition, Choosing the Right Walls, and Doors You Can’t See Yet

Struggling with career stagnation? Explore why a career change to data analytics is about more than just tools—it's about opening doors to a future you can't see yet.

Updated 7 May 20267 min read

Career & business

We need to talk honestly: The job market and your career

Is the IT job market in crisis? Let's analyze the facts, myths about AI, and the differences between overthinking and effective action in the data analyst profession.

Updated 30 Apr 20266 min read

Career & business

When Should You Actually Lie in a Job Interview? The Brutal Truth About Recruitment

Is honesty always the best policy? Discover 5 specific situations where lying or stretching the truth in a job interview is necessary to land your dream career.

Updated 29 Apr 20269 min read

Career & business

AI Was Supposed to Replace Us. Yet the Data Tells a Different Story

Is AI really replacing jobs in tech? Data from the No Fluff Jobs report shows a surprising trend: more IT job offers, fewer applicants, and growing demand for data specialists.

Updated 9 Mar 20269 min read

Career & business

Ambition Is Not Arrogance. Why Preparation and Proactivity Actually Matter

Why ambition is often confused with arrogance and how preparation and proactivity shape long-term career growth without motivational nonsense.

Updated 12 Jan 20266 min read

Career & business

The Backend of Analytics, Career Switching, and the Meaning of Working with Data

What is backend data analytics and why dashboards alone are not enough? A deep interview on BI, data engineering, AI, and career switching.

Updated 12 Jan 20269 min read

Career & business

Data as the New Oil? A Real Conversation About Big Data, Scaling, AI and the Future of Tech Jobs

What is Big Data in practice? A deep conversation about data scaling, data engineering, distributed systems and how AI impacts tech careers.

Updated 7 Jan 20267 min read

Career & business

How to Find a Job in 2026. Why Old Strategies No Longer Work

The job market has changed more than you think. Learn how to find a job in 2026, why old strategies no longer work, and what actually increases your chances.

Updated 7 Jan 20267 min read

Career & business

From Hospitality to Big Data. A Real Story About Career Change, Flow in Data, and Living Without a Strict Work-Life Split

What does a real career change to data analytics look like? An honest story about learning Python, working with big data, doubts, flow, and growth.

Updated 7 Jan 20268 min read

Career & business

Don’t Plan Your Career Too Rigidly. A Conversation About Work, Ambition, and Freedom

Is work-life balance really a myth? A reflective conversation about work, ambition, career choices, and life in data analytics.

Updated 15 Dec 20258 min read

Career & business

Why You Can’t Get a Job: On Career Change, Competition, and the Illusion of Balance

Struggling to land a job despite your efforts? Discover why “trying” isn’t enough. I share honest insights on career change, real competition in the job market, and why the illusion of balance might be holding you back.

Updated 11 Nov 20258 min read

Career & business

Freelancer or Full-Time Employee – The Truth About a Data Analyst’s Work

Wondering whether to work as a freelance or full-time data analyst? Discover the real pros, cons, and hidden pitfalls before you make your decision.

Updated 11 Nov 20258 min read

Career & business

When Is It Too Late to Change Careers? At What Age Does a Career Switch Still Make Sense?

Is it really too late to change careers after 40? Discover when a career switch still makes sense, how to use your experience as an advantage, and why fear can be your best motivation.

Updated 11 Nov 20256 min read

Career & business

A Good Job and the Confidence You’re Missing

How do you build confidence and grow your career in data analytics? Discover my journey from customer service to data architect — about hard work, learning, and finding real confidence at work.

Updated 10 Nov 20258 min read

Career & business

How to Really Use AI in Your Job Search — From Your CV to the Interview

Learn how to use artificial intelligence to make your job search faster and more effective. From writing a powerful CV and optimizing your LinkedIn profile to practicing for interviews and building a personal job-hunting system with AI.

Updated 10 Nov 20257 min read

Career & business

Motivation Is a Lie. That’s Why You’re Not Changing Your Job.

Most people believe motivation is the key to career change — but that’s a lie. In this article, I explain why motivation fails, what truly drives a successful career transition, and how to finally change your job with a clear plan and purpose.

Updated 10 Nov 20256 min read

Career & business

A Week in the Life of a Data Analyst – What My Job Really Looks Like

Ever wondered what a typical week looks like for a data analyst? From dashboards in Power BI and Tableau to SQL, Python, and team meetings – discover what daily life as a data analyst really involves and why this career is so dynamic and rewarding.

Updated 10 Nov 20258 min read

Career & business

How to Analyze Election Polls – Understanding Statistical Error and Why Polls Can Be Wrong

Learn how election polls really work. What does the margin of error mean, why can 1,000 people represent a whole country, and why polls sometimes get it wrong.

Updated 10 Nov 20257 min read

expert

What Does a Data Engineer Do? A Candid Conversation with Nieinformatyk

Zastanawiasz się, jak wygląda codzienność inżyniera danych? W tym wywiadzie z Darkiem Butkiewiczem (NIEINFORMATYK) poznasz kulisy tej pracy, realne technologie i wskazówki dla osób myślących o przebranżowieniu.

Updated 18 Aug 20256 min read

expert

Power BI is not Excel. A conversation on implementation, Copilot and training with Iga Kwiecińska

Discover what implementing Power BI really looks like and why Copilot won’t replace analysts. Iga Kwiecińska shares practical insights on common mistakes, AI expectations and the role of live training in data analytics.

Updated 2 Aug 20256 min read

Career & business

How to Become a Data Analyst with No Experience? Izabela Witczak’s Real Story

Want to become a data analyst but have no experience? Discover how Izabela Witczak made it happen in just 9 months. Real advice, clear steps, and inspiration for your career switch into data.

Updated 11 Jul 20256 min read

Career & business

The Modern Programmer – Interview with Kamil Brzeziński

What does a programmer’s job really look like today? In this in-depth interview, Kamil Brzeziński talks about AI, vibe coding, career advice, and the evolving role of developers in the modern tech world.

Updated 26 May 20255 min read

Career & business

The Job of the Future Doesn’t Exist. Here’s Why You Should Stop Chasing It

Does the job of the future really exist? In this article, I explain why chasing trendy job titles is a trap—and what skills you should focus on instead, especially in tech and data.

Updated 6 May 20256 min read

Career & business

AI won’t take your job. It will take your loneliness.

AI may not replace your job, but it can replace your loneliness. And that might be a good thing. Here’s how artificial intelligence is becoming a new kind of emotional support system.

Updated 17 Apr 20253 min read

Career & business

How to Get Your First Job as a Data Analyst During a Market Slowdown – 5 Smart Strategies

Looking for your first job in data analytics during a slowdown? These 5 strategies will help you land a role by searching smarter, not just harder.

Updated 2 Apr 20255 min read

Career & business

AI and the Future of Data Analysis: Will AI Replace Data Analysts?

Explore the transformative potential of AI in the realm of data analysis. Discover whether AI will replace data analysts or if it will simply reshape the role.

Updated 10 Feb 20254 min read

bez kategorii

How to Successfully Transition into a Data Analyst Career: Essential Skills and Tips

Thinking about becoming a data analyst? Learn how to successfully transition into a data analyst career with these essential skills and tips.

Updated 20 Nov 20242 min read

expert

Data scientist vs data analyst - interview with Magda Kostrzewska

Main topic: data scientist vs data analyst. Magda is an experienced data analyst and data scientist, and in this interview...

Updated 26 Jul 20244 min read

expert

Interview with Jan Tymiński: The Role of DevOps in Today's IT World

DevOps is someone responsible for the infrastructure on which applications created by programmers and analytical systems provided...

Updated 26 Jul 20246 min read

Career & business

GPT 4o and Gemini Advanced or how new AI models will change the world

If you ever googled 'GPT 4o and Gemini Advanced' or you would like to know how new AI models will change the world, this article is for you.

Updated 23 May 20243 min read

Career & business

Job market crisis or is it difficult to get a job now

If you ever googled 'Job market crisis' or you would like to know is it difficult to get a job now, this article is for you.

Updated 13 May 20243 min read

Career & business

IT job market in Poland or is it still worth it to work in the tech industry

If you ever googled 'IT job market in Poland' or you would like to know is it still worth it to work in the tech industry, this article is for you.

Updated 17 Apr 20243 min read

Career & business

Motivation at work or how to change your mindset?

If you ever googled 'Motivation at work' or you would like to know how to change your mindset, this article is for you.

Updated 8 Mar 20243 min read

ChatGPT in IT: Can Artificial Intelligence Hinder Your Career?

Is using ChatGPT in IT always a good thing? Can learning programming with AI hinder your career? As an enthusiast and educator...

Updated 21 Jan 20243 min read

Career & business

Professional Burnout and Impostor Syndrome – Experience of looking for a job in IT

Domething that affects many of us, whether we're job hunting or entrenched in our careers - professional burnout & impostor syndrome...

Updated 21 Jan 20243 min read

Career & business

Becoming a Data Analyst: the best way into in IT

The truth is that today becoming a Data Analyst is the best way into in IT.Shocking, right? Well, I want to convince you...

Updated 16 Sept 20233 min read

Career & business

Average BI Developer salary. Money in IT - interesting comparison

Average BI Developer salary. Money in IT - interesting comparison. Today, we're diving into the fascinating world of...

Updated 9 Sept 20233 min read

What is the ELIZA effect, or is chat GPT conscious?

Do you ever have moments when you wonder if Chat GPT is conscious? Well, let's talk about Eliza Effect. But before we get to the heart of...

Updated 16 Jun 20233 min read