将 LAG 限制为特定的行条件

Question

我正在使用以下查询 return 给定站点 ID 本月和上个月之间的百分比差异。

SELECT 
reporting_month,
total_revenue,
invoice_count,
--total_revenue_prev,
--invoice_count_prev,
ROUND(SAFE_DIVIDE(total_revenue,total_revenue_prev)-1,4) AS actual_growth,
site_name
FROM (

SELECT DATE_TRUNC(table.date, MONTH) AS reporting_month,
        ROUND(SUM(table.revenue),2) AS total_revenue, 
        COUNT(*) AS invoice_count,
        ROUND(IFNULL(
           LAG(SUM(table.revenue)) OVER (ORDER BY MIN(DATE_TRUNC(table.date, MONTH))) ,
           0),2) AS total_revenue_prev,
        IFNULL(
           LAG(COUNT(*)) OVER (ORDER BY MIN(DATE_TRUNC(table.date, MONTH))) ,
           0) AS invoice_count_prev,
        tbl_sites.name AS site_name
FROM table
LEFT JOIN tbl_sites ON tbl_sites.id = table.site
WHERE table.site = '123'
GROUP BY site_name, reporting_month
ORDER BY reporting_month
)

这工作正常，正在打印：

reporting_month	total revenue	invoice_count	actual_growth	site_name
2020-11-01 00:00:00 UTC	100.00	10	0.571	SiteNameString
2020-12-01 00:00:00 UTC	125.00	7	0.2500	SiteNameString

不过，我希望能够运行对所有网站进行相同的查询。当我从子查询中删除 WHERE table.site = '123' 时，我假设是 LAG 的使用导致数字报告不正确。有没有办法将 LAG 限制在 'current' 行站点？

Answer 1

您只需在 LAG 语句中添加 PARTITION BY 子句即可定义 window 函数 :

LAG(SUM(table.revenue)) OVER (PARTITION BY table.site ORDER BY table.date, MONTH)

Here 是相关的 BigQuery 文档页面

“PARTITION BY：将输入行分解为单独的分区，在这些分区上独立评估分析函数。”

将 LAG 限制为特定的行条件

Restrict LAG to specific row condition

sql

google-bigquery

lag