MySQL 8.4 Release Notes
聚合函数作用于值集合。它们通常与GROUP BY子句一起使用，将值分组为子集。本节描述了大多数聚合函数。有关操作几何值的聚合函数的信息，请参见第 14.16.12 节，“空间聚合函数”。Aggregate functions operate on sets of values. They are often used
with a GROUP BY clause to group values into
subsets. This section describes most aggregate functions. For
information about aggregate functions that operate on geometry
values, see Section 14.16.12, “Spatial Aggregate Functions”.