SQLiteracy · Intermediate course · Plus
The fact table awakens: joins across a real star schema, aggregation, and the honest truth about NULL.
The Basic course kept you on one table. This one hands you the fact table: hundreds of thousands of rows of monthly airline traffic, joined to airports, carriers, and aircraft. These are the modules where SQL starts doing analysis.
This course ships with Plus, alongside the full course library. Browse the modules freely; the labs unlock when you upgrade.
Module 1 · ~22 min
Joins across the star
The fact table arrives, and tables start working together
Module 2 · ~20 min
Aggregation
GROUP BY, HAVING, and the one metric every airline watches
Module 3 · ~16 min
NULL but not void
Missing values in filters, aggregates, and this database's own design
Module 4 · ~20 min
CASE and the edge cases
Conditional logic, divide-by-zero guards, and the planes with no passengers
Module 5 · ~20 min
LEFT JOIN and what's missing
Anti-joins, unmatched keys, and the airports the fact table has never met
Finished the modules? Take the final exam: five fresh questions, no hints, and the SQLiteracy Intermediate badge when you pass them all.
Start the examWondering what you've actually learned? Review your skills across every course.
Where this data comes from
Every query in this course runs against real, public-domain data, rebuilt monthly and graded in your browser. The traffic data covers January 2025 through June 2026, and this build was last updated on 18 September 2026.
segments849,295 rowsOne row is one carrier, route, aircraft type and service class in one month. From U.S. Bureau of Transportation Statistics, T-100 Segment, public domain.
airports72,563 rowsOne row is one airport. From OurAirports, public domain.
carriers1,778 rowsOne row is one airline. From BTS lookup tables, public domain.
aircraft_types452 rowsOne row is one aircraft type. From BTS lookup tables, public domain.
countries249 rowsOne row is one country. From OurAirports, public domain.
service_classes14 rowsOne row is one service class. From BTS lookup tables, public domain.
Sources: BTS T-100, OurAirports, BTS lookups. Refreshed monthly. BTS publishes T-100 on a lag, so the most recent month here trails the calendar.