计算一个 table SQL 服务器中的项目数量（SUM Outstanding of items）

Question

我会在 SQL 服务器中询问有关总和的问题。

我有一个 table 可以存储这样的订单：

    Code     |    items    |    Kinds      |   Qty  |
-------------+-------------+---------------+--------+
PUR/2004/001 |    b001     |    PURCHASE   |   5    |
PUR/2004/001 |    b002     |    PURCHASE   |   10   |
PUR/2004/002 |    b001     |    PURCHASE   |   3    |
REC/2004/001 |    b001     |    RECEIVE    |   4    |

我需要的是一个查询来计算 table.

上每个项目的剩余余额

我想要的结果是这样的：

    items    |  Outstanding Order  |
-------------+---------------------+
    b001     |          4          |
    b002     |          10         |

Answer 1

我们可以在这里使用条件聚合：

SELECT
    items,
    SUM(CASE WHEN Kinds = 'PURCHASE' THEN Qty ELSE 0 END) -
        SUM(CASE WHEN Kinds = 'RECEIVE' THEN Qty ELSE 0 END) AS [Outstanding Order]
FROM yourTable
GROUP BY
    items;

Demo

Answer 2

有点不同的条件聚合方式：

SELECT
    items,
    SUM(CASE WHEN Kinds = 'PURCHASE' THEN Qty
             WHEN Kinds = 'RECEIVE'  THEN -Qty
        END) AS [Outstanding Order]

FROM Table1
GROUP BY
    items;

结果：

items   Outstanding Order
b001    4
b002    10

DEMO