我已经按照讲师在我正在参加的证书课程中显示的方式输入了以下查询,但是当我运行查询时,第一行几乎显示为空白,如下所示:()。尽管输入了完全相同的内容,但讲师似乎并未出现此问题,并且我不确定如何解决它。
请帮忙!
选择 用户类型, CONCAT(start_station_name," to ",end_station_name) AS 路线, COUNT(*) AS num_trips, ROUND(AVG(CAST(tripduration AS int64)/60),2) AS 持续时间 从
bigquery-public-data.new_york_citibike.citibike_trips
通过...分组
起始站名称、结束站名称、用户类型
订购依据
num_trips DESC
限制10
我成功运行了查询,但我在结果中看到一个“空白”行,我不知道如何删除它。我期望看到 10 行完整 的数据。
尝试以下查询:
SELECT
usertype,
CONCAT(start_station_name," to ",end_station_name) AS route,
COUNT(*) AS num_trips,
ROUND(AVG(CAST(tripduration AS int64)/60),2) AS duration
FROM
bigquery-public-data.new_york_citibike.citibike_trips
where tripduration is not null
GROUP BY
start_station_name,
end_station_name,
usertype
ORDER BY
num_trips DESC
LIMIT
10
您正在查询的表似乎包含一些“空”行。通常,当我们进行数据分析时,我们想要“清理”数据。我运行了以下命令:
select (
SELECT
count(*)
FROM
bigquery-public-data.new_york_citibike.citibike_trips
where tripduration is null
) as isnull,
(
SELECT
count(*)
FROM
bigquery-public-data.new_york_citibike.citibike_trips
where tripduration is not null
) as isnotnull
发现:
为空 | 不为空 |
---|---|
5828994 | 53108721 |
所以...表中大约 10% 的行似乎无效/较差/需要过滤。