Guided Notes
Window Functions & 30-Day Readmissions
ROW_NUMBER, RANK, LAG and LEAD with PARTITION BY — and using them to build a 30-day readmission analysis, first/last events and running totals.
What window functions do
Slide 1 / 5Window functions calculate across related rows without collapsing them (unlike GROUP BY): function() OVER (PARTITION BY patient_id ORDER BY admit_date) • PARTITION BY — restart for each patient. • ORDER BY — the order inside each patient. Perfect for 'next visit', 'previous result', 'first diagnosis', 'running total' questions that healthcare is full of.