mysql - 选择大小写不工作 #1064

Question

我有一个问题

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

谁能帮忙？

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

Answer 1

*应该先于你的 CASE satement，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，查询生成笛卡尔积。如果这不是您想要的，那么您需要提供链接条件，例如

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

哪里columnName是定义它们关系的列。