如果你想在WHERE子句中使用别名，你需要将它包装在一个子选择中，或CTE:

WITH LogDateDiff AS
(
   SELECT logcount, logUserID, maxlogtm
      , DATEDIFF(day, maxlogtm, GETDATE()) AS daysdiff
   FROM statslogsummary
)
SELECT logCount, logUserId, maxlogtm, daysdiff
FROM LogDateDiff
WHERE daysdiff > 120

SELECT
   logcount, logUserID, maxlogtm,
   DATEDIFF(day, maxlogtm, GETDATE()) AS daysdiff
FROM statslogsummary
WHERE ( DATEDIFF(day, maxlogtm, GETDATE() > 120)

通常不能在WHERE子句中引用字段别名。(可以把它看作包括别名在内的整个SELECT应用在WHERE子句之后。)

但是，正如在其他回答中提到的，您可以强制SQL将SELECT处理为在WHERE子句之前处理。这通常用圆括号来强制逻辑操作顺序或使用公共表表达式(CTE):

括号/子查询:

SELECT
   *
FROM
(
   SELECT
      logcount, logUserID, maxlogtm,
      DATEDIFF(day, maxlogtm, GETDATE()) AS daysdiff
   FROM statslogsummary   
) as innerTable
WHERE daysdiff > 120

或者看看亚当的CTE版本的答案。

如果你想在WHERE子句中使用别名，你需要将它包装在一个子选择中，或CTE:

WITH LogDateDiff AS
(
   SELECT logcount, logUserID, maxlogtm
      , DATEDIFF(day, maxlogtm, GETDATE()) AS daysdiff
   FROM statslogsummary
)
SELECT logCount, logUserId, maxlogtm, daysdiff
FROM LogDateDiff
WHERE daysdiff > 120

HAVING适用于MySQL 根据文件:

HAVING子句被添加到SQL中，因为WHERE关键字不能 与聚合函数一起使用。

如果你不想在CTE中列出你所有的列，另一种方法是使用outer apply:

select
    s.logcount, s.logUserID, s.maxlogtm,
    a.daysdiff
from statslogsummary as s
    outer apply (select datediff(day, s.maxlogtm, getdate()) as daysdiff) as a
where a.daysdiff > 120

来到这里看起来类似，但有一个CASE WHEN，并像这样使用where结束:where (CASE WHEN COLUMN1=COLUMN2 THEN '1' ELSE '0' END) = 0也许你可以直接在where中使用DATEDIFF。 喜欢的东西:

SELECT logcount, logUserID, maxlogtm
FROM statslogsummary
WHERE (DATEDIFF(day, maxlogtm, GETDATE())) > 120