创建一个包含 2 行值的报告，每行来自一个单独的 SELECT 语句

Question

我有一份报告（如果您愿意，可以使用Blazer），其中显示了jobs 表中最近更新或创建的行的类似数据：

5 Minutes | 1 Hour | 1 Day | Total
----------------------------------
        0        0     367  30,989

SQL 看起来像这样：

SELECT
    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '5 minutes' AND NOW()
    ) as "5 Minutes",
    
    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Hours' AND NOW()
    ) as "1 Hour",

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Day' AND NOW()
    ) as "1 Day",

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    ) as "Total"
;

我想为工作WHERE "Jobs"."active" IS TRUE 添加第二行。如何让这个显示另一行？

我希望最终结果是这样的：

Status | 5 Minutes | 1 Hour | 1 Day | Total
-------------------------------------------
*                0        0     367  30,989
Active           0        0     123  24,972

标签不是问题。唯一不明显的是如何创建新行。

Answer 1

最简单的方法是对另一组查询进行 UNION，这些查询具有更严格的 where 子句：

SELECT
    '*' as Kind,

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '5 minutes' AND NOW()
    ) as "5 Minutes",
    
    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Hours' AND NOW()
    ) as "1 Hour",

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Day' AND NOW()
    ) as "1 Day",

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    ) as "Total"

UNION ALL

SELECT
    'Active', 

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."IsActive" IS TRUE AND "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '5 minutes' AND NOW()
    ) as "5 Minutes",
    
    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."IsActive" IS TRUE AND "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Hours' AND NOW()
    ) as "1 Hour",

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."IsActive" IS TRUE AND "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Day' AND NOW()
    ) as "1 Day",

    (SELECT COUNT(*)
    FROM public.jobs AS "Jobs"
    WHERE "Jobs"."IsActive" IS TRUE 
    ) as "Total"

Answer 2

如果我是你，我更喜欢用这种方式来解决你的问题：

select
  "Jobs"."active" as Status,
  sum(case when "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '5 minutes' AND NOW() then 1 else 0 end) as "5 Minutes",
  sum(case when "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Hours' AND NOW() then 1 else 0 end) as "1 Hour",
  sum(case when "Jobs"."updated_at" "Jobs"."updated_at" BETWEEN NOW() - INTERVAL '1 Day' AND NOW() then 1 else 0 end) as "1 Day",
  count(*) as "Total"
from public.jobs AS "Jobs"
group by "Jobs"."active"

通过这种方式，您可以读取您的表格 public.jobs 一次，而不是多次（每个 count 一次）。有了这个选择，按status 分组就是一个简单的group by 操作

Answer 3

基本上，您需要条件聚合。在 Postgres 中，这通常会使用 filter:

SELECT COUNT(*) FILTER (WHERE j."updated_at" BETWEEN NOW() - INTERVAL '5 minute' AND NOW()) as cnt_5_minutes,
       COUNT(*) FILTER (WHERE j."updated_at" BETWEEN NOW() - INTERVAL '1 hour' AND NOW()) as cnt_1_hour,
       COUNT(*) FILTER (WHERE j."updated_at" BETWEEN NOW() - INTERVAL '1 day' AND NOW()) as cnt_1_day,
       COUNT(*) as Total
FROM public.jobs j;

您可能没有未来的更新日期，因此可以更简单地写为：

SELECT COUNT(*) FILTER (WHERE j."updated_at" >= NOW() - INTERVAL '5 minute') as cnt_5_minutes,
       COUNT(*) FILTER (WHERE j."updated_at" >= NOW() - INTERVAL '1 hour') as cnt_1_hour,
       COUNT(*) FILTER (WHERE j."updated_at" >= NOW() - INTERVAL '1 day') as cnt_1_day,
       COUNT(*) as Total
FROM public.jobs j;

另外，我建议你去掉updated_at 的双引号。在标识符周围使用双引号只是一个坏习惯。

Answer 4

唯一不明显的是如何创建新行。

基本上，使用UNION ALL 添加第二行。

不过，首先要摆脱每个指标的所有单独的 SELECT 查询。那是不必要的昂贵（如果桌子不是很小，这很重要）。带有条件聚合的单个SELECT 可以替换您的所有原始内容（如 Gordon 建议的那样）。在 Postgres 9.4 或更高版本中，aggregate FILTER 子句 是要走的路。见：

• Aggregate columns with additional (distinct) filters

要获得另一行，您可以运行另一个查询，将过滤器 "active" IS TRUE 添加到每个表达式（归结为 active，因为 boolean 列不需要进一步评估）。

但这会使成本再次翻倍，我们可以避免这种情况。在CTE 中运行单个SELECT，并在外部查询中使用UNION ALL 分割结果：

WITH cte AS (
   SELECT count(*) FILTER (WHERE updated_at > now() - interval '5 min')             AS ct_5min
        , count(*) FILTER (WHERE updated_at > now() - interval '5 min' AND active)  AS ct_5min_a
        , count(*) FILTER (WHERE updated_at > now() - interval '1 hour')            AS ct_1h
        , count(*) FILTER (WHERE updated_at > now() - interval '1 hour' AND active) AS ct_1h_a
        , count(*) FILTER (WHERE updated_at > now() - interval '1 day')             AS ct_1d
        , count(*) FILTER (WHERE updated_at > now() - interval '1 day' AND active)  AS ct_1d_a
        , count(*)                       AS ct_all
        , count(*) FILTER (WHERE active) AS ct_all_a
   FROM   public.jobs
   )
SELECT '*' AS status, ct_5min, ct_1h, ct_1d, ct_all
FROM   cte
UNION ALL
SELECT 'Active', ct_5min_a, ct_1h_a, ct_1d_a, ct_all_a
FROM   cte