Question

我遇到了这个问题

SELECT
CASE WHEN QuantityPart =< Threshold
               THEN (Threshold - QuantityPart) + Threshold
       END as RecommendedReorderQuantity, *
FROM parts, stock

任何人都可以帮忙吗？

SELECT *, 
       CASE WHEN QuantityPart =< Threshold 
            THEN (Threshold - QuantityPart) + Threshold 
       END as RecommendedReorderQuantity 
FROM parts INNER JOIN stock 
        ON parts.PartID = stock.PartID

Answer 1

*应该在CASE sattement之前出现，还有一件事，应该是

<= 不 =<

SELECT *, 
       CASE WHEN QuantityPart <= Threshold 
            THEN (Threshold - QuantityPart) + Threshold 
       END as RecommendedReorderQuantity 
FROM parts, stock

作为旁注，查询产生笛卡尔积。如果这不是你想要的，那么你需要提供链接条件，ex

SELECT *, 
       CASE WHEN QuantityPart <=  Threshold 
            THEN (Threshold - QuantityPart) + Threshold 
       END as RecommendedReorderQuantity 
FROM parts INNER JOIN stock 
        ON parts.columnName = stock.columnName

其中columnName是定义其关系的列。

Answer 2

此外，安全的做法是指定else条件，即使是微不足道的。

Answer 3

替换=＆lt;与＆lt; =

选择当QuantityPart＆lt; =阈值时的情况那么（门槛 - 数量部分）+门槛 END作为RecommendedReorderQuantity，* 从零件，库存

选择案例不起作用＃1064

3 个答案: