Question

我正在运行以下查询..

Select T1.* from T1 
LEFT JOIN T2 ON T1.C1 = T2.C1 
LEFT JOIN T3 ON T2.C3 = T3.C3
ORDER BY Case When T1.C1 = 'ABC' THEN 'XYZ' END  AS COMMENTS

它在AS附近给我一个语法错误。无法弄清楚错误。

Answer 1

在按

的顺序使用案例时，您不需要AS别名

Select T1.* from T1 
LEFT JOIN T2 ON T1.C1 = T2.C1 
LEFT JOIN T3 ON T2.C3 = T3.C3
ORDER BY Case When T1.C1 = 'ABC' THEN 'XYZ' END

Answer 2

这是因为你试图为ORDER BY子句分配一个别名 - 这是不允许的，我不确定你想在这里实现什么？

您需要：

Select T1.* from T1 
LEFT JOIN T2 ON T1.C1 = T2.C1 
LEFT JOIN T3 ON T2.C3 = T3.C3
ORDER BY Case When T1.C1 = 'ABC' THEN 'XYZ' END

或者，如果您希望在SELECT中返回CASE值，则需要：

Select T1.*, Case When T1.C1 = 'ABC' THEN 'XYZ' END AS COMMENTS
from T1 
    LEFT JOIN T2 ON T1.C1 = T2.C1 
    LEFT JOIN T3 ON T2.C3 = T3.C3
ORDER BY Case When T1.C1 = 'ABC' THEN 'XYZ' END

此外，再次不确定这里的意图，所以它取决于，但你可能需要一个ELSE在那个案例... e.g。

ORDER BY CASE WHEN T1.C1 = 'ABC' THEN 'XYZ' ELSE T1.C1 END

SQL SERVER 2005案例结束时

2 个答案: