intermediate~4h
Window Functions — ROW_NUMBER, RANK, LEAD, LAG
Window functions perform calculations across rows related to the current row WITHOUT collapsing the result into a single row (unlike GROUP BY aggregates). They are one of the most powerful SQL feature
Learning objectives
- Explain what a window function can do that GROUP BY fundamentally cannot.
- Distinguish ROW_NUMBER, RANK, and DENSE_RANK by how each handles ties.
- Use LEAD and LAG to compare a row against a neighboring row without a self-join.
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Window Functions — ROW_NUMBER, RANK, LEAD, LAG