使用MySql公式的建议

Question

select v1.Value1 - v2.Value2 
from (Select Amt as Value1 
      from lineitem 
      WHERE item ='test1' and type='receiving') 
      as v1 CROSS JOIN (Select Amt as Value2 
                        from lineitem 
                        WHERE item ='test1' and type='shipping') 
                        as v2;

此脚本未返回任何内容。我要做的是从收货和运输中减去同一张桌子上的Amts。有什么建议吗？

Answer 1

SELECT sum(case when type='receiving' then amt else -amt end)
    FROM lineitem WHERE item='test1' AND type IN ('receiving','shipping')