Select 最新可用 SQL 条目状态

Question

考虑这个 DDL：

CREATE TABLE cash_depot_state 
(
    id INTEGER NOT NULL PRIMARY KEY,
    date DATE,
    amount REAL,
    cash_depot_id INTEGER
);
    
INSERT INTO cash_depot_state (date, amount, cash_depot_id) 
VALUES (DATE('2022-03-02'), 382489, 5);
INSERT INTO cash_depot_state (date, amount, cash_depot_id) 
VALUES (DATE('2022-03-03'), 750, 2);
INSERT INTO cash_depot_state (date, amount, cash_depot_id) 
VALUES (DATE('2022-03-04'), 750, 3);
INSERT INTO cash_depot_state (date, amount, cash_depot_id) 
VALUES (DATE('2022-03-05'), 0, 5);

对于日期数组，我需要 select 所有现金仓库的实际金额总和：

2022-03-01 - 无可用数据 - 预计 0
2022-03-02 - 现金仓库 #5 已将其值更改为 382489 - 预计为 382489
2022-03-03 - 现金仓库 #2 已将其值更改为 750 - 预计为 382489 + 750
2022-03-03 - 现金仓库 #3 已将其值更改为 750 - 预计 382489 + 750 + 750
2022-03-04 - 现金仓库 #5 已将其值更改为 0 - 预计 0 + 750 + 750

我最好的尝试：http://sqlfiddle.com/#!5/94ad0d/1

但我不知道如何挑选子组的获胜者

Answer 1

您可以将每个现金仓库的最新金额定义为行号为 1 的记录，当您按 cash_depot_id 划分记录时，并按 date 降序排列：

SELECT 
    id,
    cash_depot_id,
    date,
    amount,
    ROW_NUMBER() OVER (PARTITION BY cash_depot_id ORDER BY date DESC) rn
FROM
    cash_depot_state

这将突出显示来自您的 table 的最新数据 - 所有相关行都将具有 rn = 1:

id	cash_depot_id	date	amount	rn
2	2	2022-03-03	750.0	1
3	3	2022-03-04	750.0	1
4	5	2022-03-05	0.0	1
1	5	2022-03-02	382489.0	2

现在您可以使用 WHERE 子句来过滤特定日期的记录，例如WHERE data <= '2022-03-05':

SELECT
    SUM(amount) sum_amount
FROM
    (
        SELECT amount, ROW_NUMBER() OVER (PARTITION BY cash_depot_id ORDER BY date DESC) rn
        FROM   cash_depot_state 
        WHERE  date <= '2022-03-05'
    ) latest
WHERE
    rn = 1;

将 return 1500.

解决这个问题的更传统的方法是关联 sub-query:

SELECT
    SUM(amount) sum_amount
FROM
    cash_depot_state s
WHERE
    date = (
        SELECT MAX(date)
        FROM   cash_depot_state
        WHERE  date <= '2022-03-05' AND cash_depot_id = s.cash_depot_id
    )

或针对具体化 sub-query 的联接：

SELECT
    SUM(amount) sum_amount
FROM
    cash_depot_state s
    INNER JOIN (
        SELECT   MAX(date) date, cash_depot_id
        FROM     cash_depot_state
        WHERE    date <= '2022-03-05' 
        GROUP BY cash_depot_id
    ) latest ON latest.cash_depot_id = s.cash_depot_id AND latest.date = s.date

在大型 table 中，这些可能比 ROW_NUMBER() 变体更快。 YMMV，测量一下。

涵盖 date、cash_depot_id 和 amount 的索引有助于所有显示的方法：

CREATE INDEX ix_latest_cash ON cash_depot_state (date DESC, cash_depot_id ASC, amount);

运行针对生成日历的 CTE，以上任何一项都可以作为子查询关联

WITH RECURSIVE dates(date) AS (
  SELECT '2022-03-01'
  UNION ALL
  SELECT date(date, '+1 day') FROM dates WHERE date < DATE('now')
)
SELECT
    date,
    IFNULL(
        (
            -- any of the above approaches with `WHERE date <= dates.date`
        ), 0
    ) balance
FROM
    dates;

例如http://sqlfiddle.com/#!5/94ad0d/12

Select 最新可用 SQL 条目状态

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