SQL (Structured Query Language) is the lingua franca of databases. It was standardized in 1986 and has stayed remarkably stable since: the SELECT, JOIN, GROUP BY, and aggregate-function clauses you wrote against MySQL ten years ago still work against Postgres, BigQuery, Snowflake, DuckDB, and SQLite today. New SQL dialects keep adding features (window functions, JSON paths, CTEs, lateral joins, MERGE) but the core has barely moved.
What separates a junior SQL author from a senior one is rarely syntax. It's the ability to read execution plans, choose indexes that match query patterns, decide when a CTE blocks predicate pushdown, and know which queries belong in OLTP vs which should run against an analytics warehouse. Most production performance problems are SQL problems in disguise.
What you'll work with in these 34 courses
- Core SQL: SELECT, JOIN types, GROUP BY, HAVING, subqueries
- Window functions:
ROW_NUMBER,LAG,LEAD, partitioned aggregates - CTEs and recursive queries (org charts, graph traversal)
- Indexes: B-tree, GIN, BRIN, partial and expression indexes
- Query planning: EXPLAIN ANALYZE, statistics, plan-stability tricks
- Modern features: JSON columns, full-text search, MERGE, UPSERT
SQL is one of the few skills that survives every framework rewrite. Whether you work with PostgreSQL, MySQL, SQL Server, BigQuery, Snowflake, Redshift, or DuckDB, the time invested compounds across every job for the rest of your career.
