Sql 引用在“选择”中创建的自定义列

我想引用上面创建的列简写名称，以大大简化

DATE\u DIFF

行的可读性，但我不确定这是否允许

---

下面的代码可能吗？请注意，

DATE\u DIFF

的输入是在前面的两行中启动的

SELECT DISTINCT
    Stuff ,
    DATE_FORMAT(FROM_UNIXTIME(date1), '%Y-%d-%m') as Date_Start ,
    DATE_FORMAT(FROM_UNIXTIME(date2), '%Y-%d-%m') as Date_End  ,
    DATE_DIFF( 'day' , Date_Start , Date_End) + 1 as Date_Delta ,    `<-- HERE
    More_Stuff 
FROM T1
LEFT JOIN T2
    ON Stuff = More_Stuff
LEFT JOIN T3
    ON More_Stuff = Other_Stuff

选择DISTINCT
东西
日期格式（从UNIXTIME（date1），“%Y-%d-%m”）作为日期开始，
日期格式（从UNIXTIME（date2），“%Y-%d-%m”）作为日期结束，
DATE_DIFF（'day'，DATE_Start，DATE_End）+1作为DATE_Delta，`您可能会看到：

SELECT
    Stuff
    , Date_Start
    , Date_End
    , DATE_DIFF( 'day' , Date_Start , Date_End) + 1 as Date_Delta
    , More_Stuff
FROM
    (
        SELECT DISTINCT
            Stuff ,
            DATE_FORMAT(FROM_UNIXTIME(date1), '%Y-%d-%m') as Date_Start ,
            DATE_FORMAT(FROM_UNIXTIME(date2), '%Y-%d-%m') as Date_End  ,
            DATE_DIFF( 'day' , Date_Start , Date_End) + 1 as Date_Delta ,
            More_Stuff 
        FROM T1
        LEFT JOIN T2
            ON Stuff = More_Stuff
        LEFT JOIN T3
            ON More_Stuff = Other_Stuff
    ) as Q

或：

要在
SELECT
部分中使用字段，它必须存在于
FROM
部分中。
这是令人失望的。不过，感谢你证实了我的恐惧！
SELECT DISTINCT
    Stuff ,
    DATE_FORMAT(FROM_UNIXTIME(date1), '%Y-%d-%m') as Date_Start ,
    DATE_FORMAT(FROM_UNIXTIME(date2), '%Y-%d-%m') as Date_End  ,
    DATE_DIFF( 'day' , DATE_FORMAT(FROM_UNIXTIME(date1), '%Y-%d-%m') , DATE_FORMAT(FROM_UNIXTIME(date2), '%Y-%d-%m')) + 1 as Date_Delta ,
    More_Stuff 
FROM T1
LEFT JOIN T2
    ON Stuff = More_Stuff
LEFT JOIN T3
    ON More_Stuff = Other_Stuff