Message in Chinese (Simplified) (中文(简体))
聚合不能出现在 ON 子句中，除非该子句位于 HAVING 子句或选择列表所包含的子查询中，并且所聚合的列是外部引用。
Unlocalized message
An aggregate cannot appear in an ON clause unless it is in a subquery contained in a HAVING clause or select list, and the column being aggregated is an outer reference.
Search by Google