8623: The query processor ran out of internal resources and could not produce a query plan
SQL ServerWhat does it mean?
The query processor exhausted its internal resources for an overly complex query and could not produce an execution plan. The query cannot be optimized because it is too large/complex.
Why does it happen?
Queries with very long IN lists or many OR/UNION clauses, an excessive number of JOINs, huge auto-generated queries, queries with too many parameters, or excessively deep expression trees.
How to fix it
Simplify the query: move long IN lists into a temp table/table-valued parameter, reduce OR conditions with UNION ALL or a rewrite, and split the complex query into parts. Reduce the number of JOINs. Batch auto-generated queries. Review indexes and query design when needed.