PostgreSQL HAVING 子句
HAVING 子句可以让我们筛选分组后的各组数据。
WHERE 子句在所选列上设置条件，而 HAVING 子句则在由 GROUP BY 子句创建的分组上设置条件。
语法
下面是 HAVING 子句在 SELECT 查询中的位置：
SELECT
FROM
WHERE
GROUP BY
HAVING
ORDER BY
HAVING 子句必须放置于 GROUP BY 子句后面，ORDER BY 子句前面，下面是 HAVING 子句在 SELECT 语句中基础语
