SQL Guides
Concise, example-driven guides for every SQL concept you need as a business analyst.
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Sign up freeSQL Tip of the Day
Use NULLIF(denominator, 0) instead of checking WHERE denominator != 0 — it keeps your row and returns NULL for the ratio instead of erroring or dropping the row entirely.
SQL Foundations
SELECT basics, WHERE filters, ORDER BY, and LIMIT — the four building blocks every analyst needs.
Aggregations & GROUP BY
COUNT, SUM, AVG, MIN, MAX and how to group data into business summaries with HAVING.
Joins & Relationships
Connect tables with INNER JOIN, LEFT JOIN, and self-joins. Know which to use and why.
Subqueries
Scalar subqueries, correlated subqueries, EXISTS, and IN — queries inside queries.
Window Functions
ROW_NUMBER, RANK, LAG/LEAD, and rolling averages — analytics SQL that doesn't collapse your rows.
Date & Time
DATE_TRUNC, EXTRACT, INTERVAL arithmetic, and timezone handling for time-series business data.
CTEs & WITH Clause
Write readable, maintainable queries with Common Table Expressions — including chained and recursive CTEs.
Business Metrics in SQL
CAC, LTV, churn rate, retention, and MRR waterfall — the metrics that drive SaaS and growth decisions.
8 guides · updated regularly