SQL
coreFoundations: Ground yourself in SQL, source systems, business metrics, and warehouse basics.
What it is
SQL analysis turns raw relational and event data into cohorts, funnels, user journeys, reporting tables, and defensible business metrics.
Why it matters
SQL is still the shared language across BI, product analytics, data engineering, governance, health analytics, and OR work. The practical bar is not syntax; it is avoiding double-counts, fanout joins, stale filters, and silent null bugs.
Proof to build
Solve a cohort or funnel analysis from raw tables, include validation queries, and explain how you checked row grain, duplicates, nulls, and date boundaries.
LDS resources
External references