Guided Notes
Counting & Summarizing with GROUP BY
COUNT, SUM, AVG, MIN, MAX, COUNT(DISTINCT), GROUP BY and HAVING — answering 'how many and how much by group' questions on encounters.
Aggregate functions
Slide 1 / 5• COUNT(*) — number of rows. • COUNT(DISTINCT patient_id) — number of unique patients. • SUM(total_charges), AVG(...), MIN(...), MAX(...). • Aggregates ignore NULLs (except COUNT(*)).
SELECT COUNT(*) AS encounters, COUNT(DISTINCT patient_id) AS patients FROM encounters;