Scalar Functions — Window

Window functions compute values relative to neighboring rows within a result set. All five dialects support the full set of KQL window functions — they map directly to standard SQL window function syntax using OVER () clauses.

Legend: ✅ Supported · ⚠️ Approximated · ❌ Not Supported · 🔄 Rewritten

Function	SQLite	MySQL	ClickHouse	PostgreSQL	DuckDB	Notes
`row_number()`	✅	✅	✅	✅	✅	`row_number() OVER ()`
`rank()`	✅	✅	✅	✅	✅	`RANK() OVER ()`
`dense_rank()`	✅	✅	✅	✅	✅	`DENSE_RANK() OVER ()`
`prev()`	✅	✅	✅	✅	✅	`LAG() OVER ()`
`next()`	✅	✅	✅	✅	✅	`LEAD() OVER ()`
`row_cumsum()`	✅	✅	✅	✅	✅	`SUM() OVER (ROWS UNBOUNDED PRECEDING)`
`row_rank()`	✅	✅	✅	✅	✅	`DENSE_RANK() OVER (ORDER BY col)`