在 SQL 中增加 HAVING 子句原因是，WHERE 关键字无法与聚合函数一起使用。
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name
HAVING aggregate_function(column_name) operator value原文：https://www.cnblogs.com/yusuf/p/13321551.html