我想计算仓库中的物品并计算仓库中的可用空间,然后输出到带有 Inshelf 和 free 列的表中,我想出了类似的东西。
SELECT COUNT(*) as Inshelf, free=10-Inshelf
FROM stock.stockproduct
WHERE StockNum = 1
AND checkOutData is NULL;
似乎它不起作用,对于这种问题有什么简单的解决方案吗?
这是行不通的 - 聚合函数的结果(例如count()
)在考虑完所有记录之后才可用。您需要使用子查询,在子查询中进行计数,在外部进行减法。在不知道您的数据库架构的情况下,这充其量只是一个猜测,但是......
SELECT InShelf, free - InShelf
FROM (
SELECT count(*) AS Inshelf, free
FROM stockproduct
WHERE StockNum = 1 AND checkOutData IS NULL
GROUP BY somefield
) AS a
工作 !!
SELECT InShelf, 10 - InShelf
FROM (
SELECT count(*) AS Inshelf, count(*) AS free
FROM stock.stockproduct
WHERE StockNum = 1 AND checkOutData IS NULL
) AS a;
谢谢大家,对不起,我很愚蠢=.='