别名列的 Where 子句

Question

我有一个从列中解析字符串值的查询：

SELECT left(DateTimeSent, 17) AS timesent FROM allog_07_11_e query1 

当我做：

SELECT left(DateTimeSent, 17) AS timesent FROM allog_07_11_e query1.timesent != '0'

我得到：

Msg 207, Level 16, State 1, Line 1
Invalid column name 'timesent'.

任何想法为什么？

Answer 1

您不能在WHERE子句中引用别名。你必须做这样的事情：

select left(DateTimeSent, 17) as timesent
from allog_07_11_e
where left(DateTimeSent, 17) <> '0'

同样，您也可以使用子查询：

select *
from
(
    select left(DateTimeSent, 17) as timesent
    from allog_07_11_e
) a
where timesent <> '0'