SQL for Analysts

Every query begins with SELECT. This module covers the anatomy of a simple query, from picking columns to filtering rows and sorting the results.

Real-world data is messy and large. Learn to narrow down results with precise WHERE conditions, handle NULLs, and limit output rows for exploratory analysis.

Separate tables hold related facts. Joins let you bring those facts together, matching rows on common keys to build richer datasets.

Granular data becomes insight only when summarized. Aggregates collapse many rows into one statistic, and GROUP BY applies those summaries by category.

Sometimes a column's value depends on a rule. CASE expressions let you create new columns based on conditions, segment data, and handle exceptions inline.

Complex questions often need multiple passes at the same data. Subqueries and Common Table Expressions let you build queries inside queries, step by step.

Aggregates collapse rows; window functions keep them. Compute running totals, rankings, and moving comparisons without losing the original row context.

Not all data merging happens with joins. UNION, INTERSECT, and EXCEPT stack or compare results from separate queries, useful for deduplication and cross-checking.

Analysis often modifies data. Transactions ensure that updates, inserts, and deletes happen completely or not at all, preventing partial changes and data corruption.

Even experienced analysts write broken queries. This module synthesizes everything you know and adds mental frameworks for finding errors, understanding plans, and writing maintainable SQL.