Tutorial
Hands-on walkthroughs for SQL, Python, Excel and visualisation tools — every example is runnable, not a screenshot.
109 articles in Tutorial · Page 8 of 13
Python Pandas for Data Analysis: Getting Started Guide (2026)
Learn Python Pandas for data analysis from scratch. DataFrames, filtering, groupby, merging, data cleaning, and 5 one-liners every data analyst should know.
Product Analytics in Python: Funnel Conversion, Drop-off & User Journey Mapping
Master product funnel analysis in Python with Pandas and Plotly. Calculate step-by-step conversion rates, drop-off percentages, time-to-convert distributions, and interactive Sankey user journeys.
DATE_TRUNC vs EXTRACT in SQL: Date Functions & Syntax Guide
Master DATE_TRUNC vs EXTRACT in SQL. Learn exact syntax for monthly trends, seasonality, INTERVAL rolling windows, and avoiding the BETWEEN timestamp trap.
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 JOINs Explained with Examples: The Complete Guide
Learn every SQL JOIN type with clear examples and visual explanations. INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, self-joins, and anti-join patterns.
SQL JOIN Fan-Out: What It Is, Why SUM Breaks & 2 Proven Fixes
Learn what SQL JOIN fan-out is, why one-to-many joins silently duplicate rows and break SUM/AVG totals, and how to fix it with pre-aggregation and DISTINCT.
SQL NULL Guide: How IS NULL, COUNT & COALESCE Actually Work
Master SQL NULL: learn why = NULL fails, how COUNT(column) silently skips missing data, when to use COALESCE, and how to avoid the empty-string trap.
ROW_NUMBER vs RANK vs DENSE_RANK in SQL (Tie Examples)
Compare ROW_NUMBER vs RANK vs DENSE_RANK in SQL. See exact tie handling (1,2,3 vs 1,2,2,4 vs 1,2,2,3), deduplication patterns, and interview query examples.
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.