SQL Window Functions Explained

Window functions perform calculations across rows related to the current row. Unlike GROUP BY, they don't collapse rows—you keep the detail while adding aggregated data.

Window Function Basics#

Ranking Functions#

Aggregate Window Functions#

Moving Averages#

LAG and LEAD#

FIRST_VALUE and LAST_VALUE#

Frame Specifications#

Practical Examples#

Performance Tips#

Conclusion#

Window functions are powerful for analytics queries. They let you compare rows, calculate running totals, and rank data without losing row-level detail. Master ROW_NUMBER, LAG/LEAD, and running aggregates—they solve most common analytical needs.