如何根据时间戳（createdAt）及时生成行数（计数）的数据

Question

我有Users表。每行都有字段（列）createdAt（类型为timestamp with time zone），表示用户何时创建。我必须显示简单的折线图，它将在给定时间段（minDate，maxDate）中显示及时（每天，每周或每年）的用户数量。我知道怎么分组和例如按年份对用户进行计数，但每次计数将是今年创建的用户数量，我想要的是从开始到此日期创建的用户数量。我怎么能在postgres中做到这一点？

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这是一个代码，它只返回每天创建的用户数：

SELECT COUNT(*) AS "total", date_trunc('day',u."createdAt") as "day"
FROM "Users" u
GROUP BY "day"
ORDER BY "day"

我需要的是第二行。总计为199，第三行204，依此类推。因此，每行总计是row.toal +之前所有rows.total的总和。

Answer 1

我更喜欢使用窗口函数而不是重新查询数据。

SELECT COUNT(*) AS "dailyCount", date_trunc('day',u."createdAt") as "day",
sum(count(*)) over( order by date_trunc('day',u."createdAt"))
FROM "Users" u
GROUP BY "day"
ORDER BY "day"

Answer 2

我找到了答案：

SELECT day, "dailyCount", "dailyCount" + (SELECT COUNT(*) FROM "Users" u2 WHERE date_trunc('day',u2."createdAt") < day) as "totalCount"
FROM (
SELECT COUNT(*) AS "dailyCount", date_trunc('day',u."createdAt") as "day"
FROM "Users" u
GROUP BY "day"
ORDER BY "day"
) daily