SKILL

SQL

Write queries to pull and analyze data from databases

Beginner

Basic SELECT, WHERE, JOIN queries

Intermediate

Subqueries, aggregations, window functions

Advanced

Complex joins, CTEs, performance optimization

Practice task

Using a public dataset (Chinook/diamonds): write 5 layered queries — filter+sort, GROUP BY, JOIN two tables, subquery, CTE window function — with a comment and the result for each

Pass test

Pass test: rerun all 5 queries in a clean environment. You pass if every query runs without error, each has a comment of at most 2 sentences, results are consistent with the data, and you can explain WHERE vs HAVING using one of your own queries.

Portfolio evidence

Queries with explanation, output, and insight

Common mistake

Inefficient queries and misunderstood join logic

USED IN THESE ROLES

Data Analyst Product Analyst

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