Question

我有一个postgresql表，其中包含仓库之间不同项目（模型）的移动。

例如，以下记录表示已从仓库1到2发送了5个模型1单位：

source target model units
------ ------ ----- -----
     1      2     1     5

我正在尝试构建SQL查询以获取发送和接收的单元之间的差异，按模型分组。再举一个例子：

source target model units
------ ------ ----- -----
     1      2     1     5  -- 5 sent from 1 to 2
     1      2     2     1
     2      1     1     2  -- 2 sent from 2 to 1
     2      1     1     1  -- 1 more sent from 2 to 1

结果应为：

source target model diff
------ ------ ----- ----
     1      2     1    2   -- 5 sent minus 3 received
     1      2     2    1

我想知道这是否可能使用单个SQL查询。

以下是表创建脚本和一些数据，以防万一有人想尝试：

CREATE TEMP TABLE movements
(
    source  INTEGER,
    target  INTEGER,
    model   INTEGER,
    units   INTEGER
);

insert into movements values (1,2,1,5);
insert into movements values (1,2,2,1);
insert into movements values (2,1,1,2);
insert into movements values (2,1,1,1);

Answer 1

您可以使用两个子选择来对每个方向的运动求和，然后对这两个子查询的结果进行求和并求和：

SELECT source, target, model, SUM(units)
FROM (
    SELECT source, target, model, SUM(units) AS units
    FROM movements
    WHERE source < target
    GROUP BY source, target, model
    UNION ALL
    SELECT target, source, model, SUM(-units) AS units
    FROM movements
    WHERE source > target
    GROUP BY source, target, model
) T1
GROUP BY source, target, model

Answer 2

这可以满足您的需求吗？我没有要测试的Oracle数据库，所以我希望分组表达式的规则与MS SQL Server相同

SELECT     
 CASE WHEN source < target THEN source ELSE target END AS source,
 CASE WHEN source < target THEN target ELSE source END AS target,
 SUM(CASE WHEN source < target THEN units ELSE -units END) AS Diff, 
    model
FROM  movements
GROUP BY
 CASE WHEN source < target THEN source ELSE target END,
 CASE WHEN source < target THEN target ELSE source END,
    model

使用SQL进行分组时计算行之间的差异

2 个答案: