SQL CAST, CONVERT 比较

本文转自：http://blog.csdn.net/wobuwei/archive/2009/08/18/4458185.aspx

if (@StartTime > @EndTime)
    Set @EndTime = cast (convert (char , @ScheduleDate + 1 , 101)+' '+convert (char , @EndTime, 108) as datetime )
Else
    Set @EndTime = cast (convert (char , @ScheduleDate , 101)+' '+convert (char , @EndTime, 108) as datetime )

Set @StartTime = cast (convert (char , @ScheduleDate , 101)+' '+convert (char , @StartTime, 108) as datetime )

这条语句中的Convert,Cast 的意思,作用

Convert (data_type[,length],expression[,style])

这个转换函数一般在时间类型和字符串类型转换的时候才用到.

style格式在转换时间时候的格式如下:

    Style(2位表示年份)    |   Style(4位表示年份)    |    输入输出格式
------------------------------------------------------------------------------------------------------------
0                                | 100                            |    mon dd yyyy hh:miAM(或PM)
------------------------------------------------------------------------------------------------------------
1                                |   101    美国                 |    mm/dd/yy
------------------------------------------------------------------------------------------------------------
2                                |   102     ANSI                |    yy-mm-dd
------------------------------------------------------------------------------------------------------------
3                                |   103     英法                 |    dd/mm/yy
------------------------------------------------------------------------------------------------------------
4                                |   104     德国                 |    dd.mm.yy
------------------------------------------------------------------------------------------------------------
5                                |   105     意大利              |    dd-mm-yy
------------------------------------------------------------------------------------------------------------
6                                |   106                             |    dd mon yy
------------------------------------------------------------------------------------------------------------
7                                |   107                             |    mon dd,yy
------------------------------------------------------------------------------------------------------------
8                                |   108                             |    hh:mm:ss
------------------------------------------------------------------------------------------------------------
9                                |   109                             |    mon dd yyyy hh:mi:ss:mmmmAM(或PM)
------------------------------------------------------------------------------------------------------------
10                              |   110     美国                  |    mm-dd-yy
------------------------------------------------------------------------------------------------------------
11                              |   111     日本                  |    yy/mm/dd
------------------------------------------------------------------------------------------------------------
12                              |   112     ISO                   |    yymmdd
------------------------------------------------------------------------------------------------------------
13                              |   113      欧洲默认值      |    dd mon yyyy hh:mi:ss:mmm(24小时制)
------------------------------------------------------------------------------------------------------------
14                              |   114                             |    hh:mi:ss:mmm(24小时制)
------------------------------------------------------------------------------------------------------------
20                              |   120      ODBC 规范      |     yyyy-mm-dd hh:mi:ss(24小时制)
------------------------------------------------------------------------------------------------------------
21                              |    121                            |     yyyy-mm-dd hh:mi:ss:mmm(24小时制)

Cast(Expression as data_type) : 将某种数据类型的数据显示转换为另外一种类型.

select top 1 starttime from itemtransaction
select top 1 convert (char ,starttime+1,102) from itemtransaction
select top 1 Convert (char ,starttime,108) from itemtransaction

select top 1 cast (( convert (char ,starttime+1,102)+Convert (char ,starttime,108)) as datetime ) from itemtransaction
显示结果:

来源：https://www.cnblogs.com/denylau/archive/2010/12/01/1893371.html

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