MySQL throws ER_WINDOW_NO_SUCH_WINDOW when a window function refers to a named window (e.g. `OVER w`) that has no matching `WINDOW w AS (...)` definition in the same SELECT. The resolver cannot locate the shared specification, so the query fails before any rows are processed.
Each MySQL window function needs an OVER clause that describes its frame. You may repeat the specification inline or define a reusable named window with WINDOW <name> AS (<window-spec>) and reference it later as OVER <name>. In either case MySQL resolves the name at parse time. If you use a name that does not exist or if you mistype the name, MySQL raises ER_WINDOW_NO_SUCH_WINDOW because it cannot find the matching specification. The error happens before execution, so the query never produces a result. The simplest fix is to either add the missing definition immediately after the SELECT ... FROM clause or inline the same spec: ```sql -- fails because w is not defined SELECT id, SUM(value) OVER w AS running_total FROM metrics; -- works once the named window is defined SELECT id, SUM(value) OVER w AS running_total FROM metrics WINDOW w AS (PARTITION BY account_id ORDER BY created_at DESC); ```
Check the query for all OVER <name> usages and make sure the WINDOW clause defines that name. The WINDOW clause must appear after the FROM (and optional GROUP BY/HAVING) and before ORDER BY, for example:
WINDOW w AS (PARTITION BY customer_id ORDER BY order_date DESC)If adding the clause is not desirable, replace OVER <name> with the inline spec directly inside the OVER clause.
MySQL treats identifier names in a case-insensitive way unless they are quoted, but typos still break the linkage.
WINDOW max_date AS (ORDER BY created_at DESC)
SELECT sales_id,
MAX(amount) OVER maxdate -- typo: should be max_date
FROM sales;Spelling mistakes or renaming a window without touching every reference will produce the same error. Search for the name and normalize them to the defined identifier.
If you only reuse a given window once, defining a named window can be overkill and introduces another place to keep in sync. You can eliminate the issue entirely by writing the spec inline:
SELECT
AVG(value) OVER (PARTITION BY category ORDER BY created_at ROWS BETWEEN 3 PRECEDING AND CURRENT ROW)
FROM events;Using inline OVER clauses avoids ER_WINDOW_NO_SUCH_WINDOW because there is no name resolution step.
Named windows can refer to other named windows, but the graph must remain acyclic and every referenced name must still be defined. If you see ER_WINDOW_NO_SUCH_WINDOW inside a WINDOW clause, check that any inherited parent window exists as well.
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