Mysql select查询中获取的两列的差异

我获取了两列

checkin\u date

和

booking\u time

，如下所示。如何获得这样创建的两列的差异

SELECT CAST(CONCAT(MID(Checkin,7,4) , '-' 
  , MID(Checkin,1,2)  , '-' 
  , MID(Checkin,4,2))
 AS DATETIME) as Checkin_Date,

 CAST(CONCAT(MID(Book_Time,7,4) , '-' 
  , MID(Book_Time,1,2)  , '-' 
  , MID(Book_Time,4,2))
 AS DATETIME) as Booking_Date

FROM rl_transactional.mydb

在从rl\u transactional.mydb执行

之前，我尝试执行
签入日期-预订日期
，但出现错误

错误代码：1064。您的SQL语法有错误；查看与MySQL服务器版本相对应的手册，了解第16行“Checkin_Date-Booking_Date FROM rl_transactional.mydb”附近使用的正确语法

编辑：根据建议，我使用了下面的查询

SELECT CAST(CONCAT(MID(Checkin,7,4) , '-' 
  , MID(Checkin,1,2)  , '-' 
  , MID(Checkin,4,2))
 AS DATETIME) as Checkin_Date, 

CAST(CONCAT(MID(CheckOut,7,4) , '-' 
  , MID(CheckOut,1,2)  , '-' 
  , MID(CheckOut,4,2))
 AS DATETIME) as CheckOut_Date,

 CAST(CONCAT(MID(Book_Time,7,4) , '-' 
  , MID(Book_Time,1,2)  , '-' 
  , MID(Book_Time,4,2))
 AS DATETIME) as Booking_Date,

Checkin_Date - Booking_Date
from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-' 
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      , MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date
    FROM rl_transactional.mydb
) c,
FROM rl_transactional.mydb

我正在犯错误

错误代码：1064。您的SQL语法有错误；检查
与右边的MySQL服务器版本相对应的手册
使用“签入日期-预订日期自”附近的语法（选择
在第1行铸造（混凝土（中间）（签入，7,4），“-”

尝试运行以下查询：

SELECT 
     c.Checkin_Date, 
     c.CheckOut_Date
     c.Booking_Date,
     c.Checkin_Date - c.Booking_Date
from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-' 
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      , MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date,
     CAST(CONCAT(MID(CheckOut,7,4) , '-' 
      , MID(CheckOut,1,2)  , '-' 
      , MID(CheckOut,4,2))
     AS DATETIME) as CheckOut_Date
    FROM rl_transactional.mydb
) c;

尝试运行以下查询：

SELECT 
     c.Checkin_Date, 
     c.CheckOut_Date
     c.Booking_Date,
     c.Checkin_Date - c.Booking_Date
from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-' 
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      , MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date,
     CAST(CONCAT(MID(CheckOut,7,4) , '-' 
      , MID(CheckOut,1,2)  , '-' 
      , MID(CheckOut,4,2))
     AS DATETIME) as CheckOut_Date
    FROM rl_transactional.mydb
) c;

如果要使用别名，应将查询压缩为：

select Checkin_Date - Booking_Date from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-'
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      ,MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date
    FROM rl_transactional.mydb ) 

编辑

不能在查询中重复使用别名：

select Checkin_Date - Booking_Date from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-'
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      ,MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date
    FROM rl_transactional.mydb ) 

试试这个：

SELECT 

 Checkin_Date, 

CAST(CONCAT(MID(CheckOut,7,4) , '-' 
  , MID(CheckOut,1,2)  , '-' 
  , MID(CheckOut,4,2))
 AS DATETIME) as CheckOut_Date,

Booking_Date,

Checkin_Date - Booking_Date as Diff

from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-' 
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      , MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date,
     CheckOut
    FROM rl_transactional.mydb
) c

如果要使用别名，应将查询压缩为：

select Checkin_Date - Booking_Date from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-'
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      ,MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date
    FROM rl_transactional.mydb ) 

编辑

不能在查询中重复使用别名：

select Checkin_Date - Booking_Date from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-'
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      ,MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date
    FROM rl_transactional.mydb ) 

试试这个：

SELECT 

 Checkin_Date, 

CAST(CONCAT(MID(CheckOut,7,4) , '-' 
  , MID(CheckOut,1,2)  , '-' 
  , MID(CheckOut,4,2))
 AS DATETIME) as CheckOut_Date,

Booking_Date,

Checkin_Date - Booking_Date as Diff

from (
    SELECT CAST(CONCAT(MID(Checkin,7,4) , '-' 
      , MID(Checkin,1,2)  , '-' 
      , MID(Checkin,4,2))
     AS DATETIME) as Checkin_Date,
     CAST(CONCAT(MID(Book_Time,7,4) , '-' 
      , MID(Book_Time,1,2)  , '-' 
      , MID(Book_Time,4,2))
     AS DATETIME) as Booking_Date,
     CheckOut
    FROM rl_transactional.mydb
) c

您是否在签入日期之前加了逗号？但是，您应该在签入和预订时间之间运行DATEDIFF。您可能还需要将这些日期转换为日期。@JaydipJ编辑一个混乱的问题通常是一件好事，但在这种情况下，可能会有一个您可能无意中更正的印刷错误：-）@TimBiegeleisen谢谢，我会处理好这张纸条：）您是否在签入日期之前加了逗号？但是，您应该在签入和预订时间之间运行DATEDIFF。您可能还需要将这些日期转换为日期。@JaydipJ编辑一个混乱的问题通常是一件好事，但在这种情况下，可能会有一个您可能无意中更正的印刷错误：-）@TimBiegeleisen谢谢，我会处理这张便条：）我的目标是获取所有3列。我怎样才能在差异栏中获得签入日期和预订日期？@发烧友，只需在家长查询中选择它们。我尝试过这样做，但它给了我新的错误。我用新的代码和错误信息编辑了这篇文章。我的目标是获取所有3列。我怎样才能在差异栏中获得签入日期和预订日期？@发烧友，只需在家长查询中选择它们。我尝试过这样做，但它给了我新的错误。我用新的代码和错误信息编辑了这篇文章。sighti没有解决方案做了一些操作，结果出现了新的错误。你能帮个忙吗？我做了一些操作，结果又出了一个新错误。你能帮忙吗？