Question

我有以下SQL：

SELECT A.*, 
(SELECT answer FROM [tblAnswers] B 
WHERE  B.memberID = A.memberID AND QuestionID = 3) AS ethnicity
FROM [tblMembers] A  
WHERE 
LOWER(gender) = 'm' 
AND ethnicity = 'Sephardi'

我收到错误Invalid column name 'ethnicity'，指的是该列的最后一个引用。

问题：WHERE条款无法使用此列？

我知道，如果我执行以下操作，它就会起作用：

SELECT A.*, 
(SELECT answer FROM [tblAnswers] B WHERE  B.memberID = A.memberID AND QuestionID = 3) AS ethnicity
FROM [tblMembers] A  
WHERE
LOWER(gender) = 'm' 
AND convert(nvarchar, (SELECT answer FROM [tblAnswers] B WHERE  B.memberID = A.memberID AND QuestionID = 3)) = 'Sephardi'

Answer 1

您不能在where子句中使用“Computed”列，而不能专门引用整个计算（查询，大小写等）。

您应该加入Query表而不是子查询它：

Select A.*, B.answer
From tblMembers A
    Inner Join tblAnswers B on A.memberID = B.membeID and A.QuestionID = 3
Where Lower(gender) = 'm'
    and B.answer = 'Sephardi'

Answer 2

您不能使用您刚刚在以下SELECT子句中的WHERE子句中指定的列名。作为一般情况，您可以将其放在子查询中，然后使用列名：

SELECT * FROM
(
    SELECT A.*, 
    (SELECT answer FROM [tblAnswers] B 
    WHERE  B.memberID = A.memberID AND QuestionID = 3) AS ethnicity
    FROM [tblMembers] A  
    WHERE LOWER(gender) = 'm' 
) s
WHERE ethnicity = 'Sephardi'

此查询可能更适合JOIN：

SELECT A.*, t.answer AS ethnicity
FROM [tblMembers] A  
LEFT JOIN tblAnswers t ON b.memberID = A.memberID AND QuestionID = 3
WHERE LOWER(gender) = 'm' AND t.answer = 'Sephardi'

SQL'无效列名'错误，内部选择

2 个答案: