在oracle中where关键字是无法和聚合函数一起使用的，having可以让我们筛选分组后的各组数据。
用法：
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;
例子：
SELECT
count_date,
sum(count_data) count_data
from TB_COUNT_DATA
GROUP BY count_date
HAVING SUM(count_data) > 200;