Tutorial
Hands-on walkthroughs for SQL, Python, Excel and visualisation tools — every example is runnable, not a screenshot.
119 articles in Tutorial · Page 10 of 14
WHERE vs HAVING in SQL: Execution Order & Key Differences
Master WHERE vs HAVING in SQL. Learn why WHERE filters before GROUP BY, why aggregate functions fail in WHERE, and the full 7-step query execution order.
SQL Subqueries Explained: Scalar, Correlated & Syntax Guide
Master the 3 types of SQL subqueries: scalar, multi-row (IN/EXISTS), and correlated. Avoid the NOT IN NULL trap and learn when to refactor to readable CTEs.
SQL vs NoSQL: Complete Guide for Data Analysts
Understand the differences between SQL and NoSQL databases. Learn when to use each and which to learn first.
Time Series Analysis & Forecasting in Python: Trend, Seasonality & Moving Averages
Complete guide to time series analysis and forecasting in Python. Master datetime indexing, resampling, moving average smoothing, seasonal decomposition, and the Augmented Dickey-Fuller (ADF) stationarity test.
Welcome to the Topfolio Blog
Introducing the Topfolio blog — your go-to source for data analytics tutorials, career guides, interview prep, and student success stories.
API Masterclass in Python: Authentication, Pagination, and JSON to DataFrame
Call any REST API from Python — handle API keys, Basic Auth, query params, pagination, and flatten nested JSON into Pandas DataFrames.
Applied ML Cheatsheet in Python: Iris Dataset From EDA to Cross-Validation
End-to-end ML in Python on the Iris dataset — EDA, train-test split, scaling, logistic regression, decision trees, and metrics.
Customer Analytics in Python: Cohort, RFM, and the First Query That Matters
Run RFM segmentation and cohort retention in Python — recency, frequency, monetary scores and a retention heatmap from transaction logs.
Python Database Connectivity: SQLite to BigQuery Without Hardcoding Passwords
Connect Python to SQLite, PostgreSQL, MySQL, Snowflake and BigQuery with SQLAlchemy and pandas read_sql — securely via .env files.