[英]How to calculate average and median of all the values of an array column in BigQuery?
[英]How to calculate median over multiple columns in Google BigQuery?
我正在创建一个查询来计算每天来自两个不同网站的访问中位数。
输出应如下所示:
+------------+---------+---------------+
| date | website | median_visits |
+------------+---------+---------------+
| 2019-04-01 | A | median_value |
| 2019-04-01 | B | median_value |
| 2019-04-02 | A | median_value |
| 2019-04-02 | B | median_value |
| 2019-04-03 | A | median_value |
| 2019-04-03 | B | median_value |
+------------+---------+---------------+
这是我的表(有 20,000 行)的样子:
+------------+---------+--------+
| date | website | visits |
+------------+---------+--------+
| 2019-04-01 | A | 10.0 |
| 2019-04-01 | B | 14.0 |
| 2019-04-02 | A | 85.0 |
| 2019-04-03 | A | 75.0 |
| 2019-04-02 | B | 3.0 |
| 2019-04-02 | B | 45.0 |
| 2019-04-01 | A | 12.0 |
| 2019-04-03 | A | 44.0 |
| 2019-04-01 | A | 99.0 |
+------------+---------+--------+
查询所需输出的最有效方法是什么? 我目前正在使用:
SELECT DISTINCT date, website, median_visits
FROM
(SELECT date, website, PERCENTILE_CONT(visits, 0.5)
OVER(PARTITION BY date, website) AS median_visits
FROM table)
下面是 BigQuery 标准 SQL - 我不能说它是最好的。 我什至不能保证它更好 - 但根据我的测试,我看到更好的执行计划和插槽使用。 因此,您可以尝试查看您的数据
#standardSQL
SELECT date, website,
(SELECT PERCENTILE_CONT(visit, 0.5) OVER()
FROM UNNEST(visits) visit LIMIT 1
) AS median_visits
FROM (
SELECT date, website, ARRAY_AGG(visits) visits
FROM `project.dataset.table`
GROUP BY date, website
)
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