如果 eventtime 存储为 timestamp :

SELECT TRUNC(eventtime, "D"), COUNT(DISTINCT userguid)
FROM your_table
GROUP BY TRUNC(eventtime, "D")
ORDER BY TRUNC(eventtime, "D");

否则如果 eventtime 存储为 string :

SELECT TRUNC(CAST(eventtime AS TIMESTAMP), "D"), COUNT(DISTINCT userguid)
FROM your_table
GROUP BY TRUNC(CAST(eventtime AS TIMESTAMP), "D")
ORDER BY TRUNC(CAST(eventtime AS TIMESTAMP), "D");

有关 TRUNC 函数，请参阅有关日期和时间函数的cloudera impala文档。

在 Impala 中，trunc（timestamp，“d”）表示查找一周的开始日期。你可以看看这里的 Impala 日期和时间函数。
例如：

select trunc(cast('2016-11-10' as timestamp), "D")
+---------------------------------------------+
| trunc(cast('2016-11-10' as timestamp), 'd') |
+---------------------------------------------+
| 2016-11-07 00:00:00                         |
+---------------------------------------------+

+---------------------------------------------+
| trunc(cast('2016-11-09' as timestamp), 'd') |
+---------------------------------------------+
| 2016-11-07 00:00:00                         |
+---------------------------------------------+

+---------------------------------------------+
| trunc(cast('2016-11-11' as timestamp), 'd') |
+---------------------------------------------+
| 2016-11-07 00:00:00                         |
+---------------------------------------------+