SQL is all about patterns
know the pattern, write the query.

The foundation — every SQL query starts here. Get this right first.

The most asked SQL concept in every tech interview — master all 4 join types.

COUNT, SUM, AVG, MIN, MAX — master these five and you can answer 40% of SQL interviews.

WHERE filters rows, HAVING filters groups — a subtle distinction that trips up 60% of candidates.

A query inside a query — the gateway to solving problems that a single SELECT can't handle.

Write SQL like a programmer — clean, readable, reusable. CTEs replace messy nested subqueries.

The SQL superpower that separates junior from senior — ROW_NUMBER, RANK, LAG, LEAD.

Clean and transform messy real-world data — CONCAT, SUBSTRING, REGEXP are daily tools in data roles.

Time-series analysis is in every data job — DATE_DIFF, EXTRACT, DATE_FORMAT are must-knows.

SQL's if-else — write conditional logic directly inside SELECT. Used in every analytics query.

Combine result sets from multiple queries — essential for reports and dashboards.

NULLs break everything — COALESCE, IFNULL, IS NULL are your safety nets in real data.