Tutorial
Hands-on walkthroughs for SQL, Python, Excel and visualisation tools — every example is runnable, not a screenshot.
109 articles in Tutorial · Page 5 of 13
Case Statement in SQL: Complete Guide to CASE WHEN & Conditional Aggregation
Master the case statement in sql: use CASE WHEN and SUM(CASE WHEN ...) to pivot data, categorize distributions, and aggregate conditionally in a single scan.
SQL Cheat Sheet: Commands, Queries, and Window Functions Reference
Bookmark this comprehensive sql cheat sheet: essential syntax for SELECT, JOINs, aggregations, Window Functions, CTEs, and query order of execution.
SQL COUNT Function: COUNT(*), COUNT(1) & COUNT(DISTINCT) Guide
Master the SQL COUNT function with examples of COUNT(*), COUNT(1), COUNT(DISTINCT), NULL handling, and conditional counting techniques.
SQL for Data Analyst: Complete Guide, Key Skills & Queries
Master SQL for data analyst roles with real-world query patterns, window functions, aggregations, cohort analysis, and practical workflows.
SQL Performance Tuning: 7 Proven Strategies to Accelerate Slow Queries
Master SQL performance tuning with execution plan analysis (EXPLAIN ANALYZE), indexing best practices, sargable queries, and join optimizations.
SQL Projects for All Levels: Beginner to Advanced Portfolio Guide
Stand out to hiring managers with these 6 real-world SQL projects for beginner, intermediate, and advanced data analysts with datasets and code.
SQL RANK Function: RANK vs DENSE_RANK vs ROW_NUMBER Guide
Master the SQL RANK function with side-by-side comparisons of RANK, DENSE_RANK, and ROW_NUMBER, PARTITION BY logic, and Top-N group queries.
Subquery in SQL: Single-Row, Correlated, and Nested Queries (with Examples)
Master subquery in sql: understand nested queries across SELECT, FROM, and WHERE clauses, correlated vs non-correlated subqueries, and performance fixes.
SUBTOTAL Formula in Excel: Subtotals That Respect Filters (Guide)
SUBTOTAL formula in Excel explained: function numbers 1–11 vs 101–111, filtered totals that stay correct, and step-by-step analyst examples with fixes.