# Mariadb Window Functions > Reference for MariaDB window functions and the OVER clause, covering ranking, value navigation, and ordered-set functions with syntax and common pitfalls. - Skill: `mariadb-corporation/mariadb-window-functions` (Agent Skill) - Install (CLI): `npx skillmds add mariadb-corporation/mariadb-window-functions` - Raw SKILL.md: https://api.skillmd.com/api/skills/mariadb-corporation/mariadb-window-functions/raw - Safety review: PASS (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Data & Analytics, SQL & Databases - Tags: Mariadb, Over Clause, Percentile, Ranking, Sql, Window Functions - Author: mariadb-corporation (https://skillmd.com/u/mariadb-corporation) - Updated: 2026-08-22 - Page: https://skillmd.com/skills/mariadb-corporation/mariadb-window-functions --- # MariaDB Window Functions *Last updated: 2026-07-20* Catalog of MariaDB's dedicated window functions and the `OVER (...)` clause, with signature and a one-line semantic summary per entry. Any aggregate function (`SUM`, `AVG`, `COUNT`, `MIN`, `MAX`, `STD`, `VARIANCE`, ...) can also run as a window function by adding `OVER (...)` — those aren't re-listed here (see the **`mariadb-aggregate-functions`** skill). `PERCENTILE_CONT` and `PERCENTILE_DISC` use the `WITHIN GROUP (ORDER BY ...)` ordered-set syntax and their canonical doc pages carry no parsable syntax block, so both are **skipped by the catalog extractor** below — see their canonical pages linked in See Also for full syntax and examples. For a function, frame form, or clause not listed here, fall back to the canonical reference at . > **Default context:** Assume MariaDB **11.8 LTS** unless the user specifies > another version. All functions in this category (window functions were > introduced in 10.2) are available in every current LTS branch (10.6, 10.11, > 11.4, 11.8); no `*(since X.Y)*` annotations apply here. ## What LLMs Often Miss | If the agent writes… | Prefer (MariaDB) | Why | | --- | --- | --- | | `SELECT * FROM t WHERE ROW_NUMBER() OVER (...) = 1` (or in `HAVING`/`GROUP BY`) | Compute the window function in a subquery or CTE, then filter in the outer query: `SELECT * FROM (SELECT *, ROW_NUMBER() OVER (...) AS rn FROM t) x WHERE rn = 1` | Window functions are evaluated after `WHERE`/`GROUP BY`/`HAVING`, and MariaDB rejects them there outright — server error: "Window function is allowed only in SELECT list and ORDER BY clause" | | Treating `ROW_NUMBER()`, `RANK()`, and `DENSE_RANK()` as interchangeable for "top N per group" | Pick deliberately: `ROW_NUMBER()` always gives distinct 1..N (arbitrarily breaks ties); `RANK()` gives ties the same value and **skips** subsequent ranks (1,2,2,4); `DENSE_RANK()` gives ties the same value with **no gaps** (1,2,2,3) | Silent correctness bug if the wrong one is picked for tie-heavy data — e.g. "top 2 per partition" behaves differently under `RANK` vs `ROW_NUMBER` when there's a tie for 2nd place | | `SUM(x) OVER (ORDER BY y)` expecting each row to see the whole partition | With an `ORDER BY` and no explicit frame, the default frame is `RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW` — a running total, not a partition-wide sum. Add an explicit frame (or drop `ORDER BY`) for a whole-partition aggregate | Classic footgun: `LAST_VALUE(x) OVER (ORDER BY y)` under the default frame returns the **current row's** value (since "last row in frame" = current row), not the partition's actual last row — use an explicit `ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING` frame to get the true last value | | `LAG(col) OVER (PARTITION BY p)` with no `ORDER BY` | `ORDER BY` is mandatory in the `OVER (...)` clause for `LAG`/`LEAD` (and for `RANK`, `DENSE_RANK`, `PERCENT_RANK`, `CUME_DIST`, `PERCENTILE_CONT`, `PERCENTILE_DISC`) — omitting it is an error. Default offset is `1`; default fill value is `NULL`; offset `0` means the current row; negative offsets flip `LAG`↔`LEAD` direction | Doc pages render `ORDER BY` in `[...]` (optional-looking) BNF for these functions, but the server enforces it — `ROW_NUMBER()`, `NTILE()`, `FIRST_VALUE`, `LAST_VALUE`, and `NTH_VALUE` are the ones that genuinely tolerate omitting it | | `MEDIAN(x) OVER (PARTITION BY p ORDER BY x)` or `PERCENTILE_CONT(0.5) OVER (ORDER BY x)` | Ordering for `MEDIAN`/`PERCENTILE_CONT`/`PERCENTILE_DISC` goes in `WITHIN GROUP (ORDER BY expr)`, not in `OVER (...)`. The `OVER (...)` clause for these three accepts **`PARTITION BY` only** — no `ORDER BY`, no frame: `PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY x) OVER (PARTITION BY p)`. `MEDIAN(x) OVER (...)` is sugar for exactly that with the percentile fixed at `0.5` | Putting `ORDER BY` inside `OVER (...)` for these functions is a parse error, not a silent no-op | | `... RANGE BETWEEN INTERVAL 1 DAY PRECEDING AND CURRENT ROW` over `ORDER BY a, b` | `RANGE`-type frames with an explicit numeric/interval bound (`n PRECEDING`/`FOLLOWING`) require the window's `ORDER BY` to be exactly **one** sort key — multiple columns are an error. `RANGE` frames also don't support `DATE`/`DATETIME` arithmetic in the bound | Use `ROWS` instead of `RANGE` for multi-column-ordered or date-arithmetic frames | | `... EXCLUDE CURRENT ROW`, a `GROUPS`-type frame, or `ORDER BY x NULLS LAST` | Not available in MariaDB. `GROUPS` frames and `NULLS FIRST`/`NULLS LAST` aren't even parsed; `EXCLUDE ...` parses but is rejected at runtime ("Frame exclusion is not supported yet") | Don't propose these as drop-in equivalents to standard-SQL frame exclusion — there's no MariaDB workaround beyond restructuring the frame bounds or a `CASE` expression | | Repeating the same `OVER (PARTITION BY ... ORDER BY ...)` for several window functions in one query | Define it once with `WINDOW w AS (PARTITION BY ... ORDER BY ...)` and reference `OVER w` per function | Also lets MariaDB's optimizer reuse a single sort pass across window functions with identical or prefix-compatible `PARTITION BY`/`ORDER BY` specs — repeating slightly different specs by hand can force extra `filesort` passes | | `AVG(DISTINCT x) OVER (...)` or `COUNT(DISTINCT x) OVER (...)` | Not supported — `DISTINCT` inside an aggregate function used as a window function is rejected. Deduplicate in a subquery first if you need distinct-value aggregation per window | Aggregate functions gain `OVER (...)` support, not full standard-SQL window-aggregate semantics | ## Functions ### CUME_DIST `CUME_DIST() OVER (` `CUME_DIST()` is a window function that returns the cumulative distribution of a given row. ### DENSE_RANK `DENSE_RANK() OVER (` `DENSE_RANK()` is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving the same result. ### FIRST_VALUE `FIRST_VALUE(expr) OVER (` `FIRST_VALUE` returns the first result from an ordered set, or NULL if no such result exists. ### LAG `LAG (expr[, offset]) OVER (` The `LAG` function accesses data from a previous row according to the `ORDER BY` clause without the need for a self-join. ### LEAD `LEAD (expr[, offset]) OVER (` The `LEAD` function accesses data from a following row in the same result set without the need for a self-join. ### MEDIAN `MEDIAN(median expression) OVER (` `MEDIAN()` is a window function that returns the median value of a range of values. ### NTH_VALUE `NTH_VALUE (expr[, num_row]) OVER (` The `NTH_VALUE` function returns the value evaluated at row number `num_row` of the window frame, starting from 1, or `NULL` if the row does not exist. ### NTILE `NTILE (expr) OVER (` `NTILE()` is a window function that returns an integer indicating which group a given row falls into. ### PERCENT_RANK `PERCENT_RANK() OVER (` `PERCENT_RANK()` is a window function that returns the relative percent rank of a given row. ### RANK `RANK() OVER (` RANK() is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving the same result. ### ROW_NUMBER `ROW_NUMBER() OVER (` `ROW_NUMBER()` is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving different row numbers. ## See Also - **`mariadb-aggregate-functions`** — `SUM`, `AVG`, `COUNT`, `MIN`, `MAX`, `STD`/`STDDEV`/`STDDEV_POP`/`STDDEV_SAMP`, `VAR_POP`/`VAR_SAMP`/`VARIANCE`, `BIT_AND`/`BIT_OR`/`BIT_XOR` — all usable as window functions via `OVER (...)` - **`mariadb-select`** — `SELECT` clause ordering (window functions evaluate after `WHERE`/`GROUP BY`/`HAVING`, before the final `ORDER BY`/`LIMIT`) - Canonical references on `mariadb.com/docs`: - - - - _This page is: Copyright © 2026 MariaDB. All rights reserved._