MariaDB 运行总计 N 和行不包括在其计算中

Question

我有一个 table，其中有 amt 和 created（时间戳）。

我正在尝试计算 amt 的运行总数，最多 N
获取计算中未包括的所有行，导致总和达到 N

我正在代码中执行此操作，但想知道是否有一种方法可以通过 SQL 获取这些信息，最好是在一个查询中。

环顾四周，很容易找到计算运行总数的示例，例如但不太容易找到运行总计 N 然后实际上只有 return 行不涉及计算 N.

Answer 1

您可以使用 window 版本的 SUM 聚合函数来获取每行的运行总数。

CREATE TABLE TEST (ID BIGINT PRIMARY KEY, AMT INT, CREATED TIMESTAMP);

INSERT INTO TEST VALUES
(1, 1, TIMESTAMP '2000-01-01 00:00:00'),
(2, 2, TIMESTAMP '2000-01-02 00:00:00'),
(3, 1, TIMESTAMP '2000-01-03 00:00:00'),
(4, 3, TIMESTAMP '2000-01-04 00:00:00'),
(5, 5, TIMESTAMP '2000-01-05 00:00:00'),
(6, 1, TIMESTAMP '2000-01-07 00:00:00');

SELECT ID, AMT, SUM(AMT) OVER (ORDER BY CREATED) RT, CREATED FROM TEST ORDER BY CREATED;

> ID AMT RT CREATED
> -- --- -- -------------------
> 1  1   1  2000-01-01 00:00:00
> 2  2   3  2000-01-02 00:00:00
> 3  1   4  2000-01-03 00:00:00
> 4  3   7  2000-01-04 00:00:00
> 5  5   12 2000-01-05 00:00:00
> 6  1   13 2000-01-07 00:00:00

然后您可以在 H2 或子查询（在 MariaDB 和 H2 中）中使用非标准 QUALIFY 子句来过滤掉低于限制的行。

如果 N 是运行总限制并且“行数不包括在计算中”是指超出限制的行数，查询将如下所示：

-- Simple non-standard query for H2
SELECT ID, AMT, SUM(AMT) OVER (ORDER BY CREATED) RT, CREATED FROM TEST
    QUALIFY RT > 10 ORDER BY CREATED;
-- Equivalent standard query with subquery for MariaDB, H2, and many others
SELECT * FROM (
    SELECT ID, AMT, SUM(AMT) OVER (ORDER BY CREATED) RT, CREATED FROM TEST
) T WHERE RT > 10 ORDER BY CREATED;

> ID AMT RT CREATED
> -- --- -- -------------------
> 5  5   12 2000-01-05 00:00:00
> 6  1   13 2000-01-07 00:00:00

这里第一行的

RT - AMT 是前面所有行的总和运行。如果您愿意，您可以单独 select：

-- Non-standard query for H2
SELECT SUM(AMT) OVER (ORDER BY CREATED) RT FROM TEST
    QUALIFY RT < 10 ORDER BY CREATED DESC FETCH FIRST ROW ONLY;
-- Non-standard query for MariaDB or H2
SELECT RT FROM (
    SELECT ID, AMT, SUM(AMT) OVER (ORDER BY CREATED) RT, CREATED FROM TEST
) T WHERE RT < 10 ORDER BY CREATED DESC LIMIT 1;
-- Standard query for H2 and others (but not for MariaDB)
SELECT RT FROM (
    SELECT ID, AMT, SUM(AMT) OVER (ORDER BY CREATED) RT, CREATED FROM TEST
) T WHERE RT < 10 ORDER BY CREATED DESC FETCH FIRST ROW ONLY;

> RT
> --
> 7

如果您有其他意思，QUALIFY 或 WHERE 标准会有所不同。

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MariaDB 运行 总计 N 和行不包括在其计算中

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MariaDB 运行总计 N 和行不包括在其计算中