Lesson 10 · 11 min
Window functions
An aggregate that doesn't collapse rows: rank, running total.
11 minLesson 10 of 10Practice includedAsk AI on any point
GROUP BY turns a group into one row. A window function computes over the group but keeps every row in place. OVER (…) defines the window: PARTITION BY splits rows into groups, ORDER BY sets the order inside. ROW_NUMBER() numbers rows, RANK() gives a rank that accounts for ties, SUM(…) OVER gives a running total, LAG() gives the value from the previous row.
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