HAVING 子句
该 HAVING 子句对通过对组进行的聚合操作生成的结果施加条件。 HAVING 子句必须跟随 GROUP BY 子句并在 ORDER BY 子句之前。
WHERE 子句根据指定的条件在聚合操作 之前 过滤行。HAVING 子句根据指定的条件在聚合操作发生 之后 过滤行。
语法
SELECT_clause FROM_clause [WHERE_clause] [GROUP_BY_clause] [HAVING_clause] [ORDER_BY_clause]
示例
返回聚合值大于指定数字的行
SELECT
MEAN("water_level") AS "mean_water_level", "location"
FROM
"h2o_feet"
GROUP BY
"location"
HAVING
"mean_water_level" > 5
返回指定时间范围内大于指定数字的平均结果
SELECT
AVG("water_level") AS "avg_water_level",
"time"
FROM
"h2o_feet"
WHERE
time >= '2019-09-01T00:00:00Z' AND time <= '2019-09-02T00:00:00Z'
GROUP BY
"time"
HAVING
"avg_water_level" > 6.82
ORDER BY
"time"