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convertcast

By Lori Barnes,2014-04-16 06:28
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convertcast

CONVERT(data_type,expression[,style])

说明:

    此样式一般在时间类型(datetime,smalldatetime)与字符串类型

    (nchar,nvarchar,char,varchar)

    相互转换的时候才用到.

例子:

    SELECT CONVERT(varchar(30),getdate(),101) now

    结果为

    now

    ---------------------------------------

    09/15/2001

    /////////////////////////////////////////////////////////////////////////////////////

style数字在转换时间时的含义如下

    -------------------------------------------------------------------------------------------------

    Style(2位表示年份) | Style(4位表示年份) | 输入输出格式

    -------------------------------------------------------------------------------------------------

    - | 0 or 100 | mon dd yyyy hh:miAM(PM)

    -------------------------------------------------------------------------------------------------

    1 | 101 | mm/dd/yy

    -------------------------------------------------------------------------------------------------

    2 | 102 | yy-mm-dd

    -------------------------------------------------------------------------------------------------

    3 | 103 | dd/mm/yy

    -------------------------------------------------------------------------------------------------

    4 | 104 | dd-mm-yy

    -------------------------------------------------------------------------------------------------

    5 | 105 | dd-mm-yy

    -------------------------------------------------------------------------------------------------

    6 | 106 | dd mon yy

    --------------------------------------------------------------------------------

-----------------

    7 | 107 | mon dd,yy

    -------------------------------------------------------------------------------------------------

    8 | 108 | hh:mm:ss

    -------------------------------------------------------------------------------------------------

    - | 9 or 109 | mon dd yyyy hh:mi:ss:mmmmAM(PM)

    -------------------------------------------------------------------------------------------------

    10 | 110 | mm-dd-yy

    -------------------------------------------------------------------------------------------------

    11 | 111 | yy/mm/dd

    -------------------------------------------------------------------------------------------------

    12 | 112 | yymmdd

    -------------------------------------------------------------------------------------------------

    - | 13 or 113 | dd mon yyyy hh:mi:ss:mmm(24小时制)

    -------------------------------------------------------------------------------------------------

    14 | 114 | hh:mi:ss:mmm(24小时制)

    -------------------------------------------------------------------------------------------------

    - | 20 or 120 | yyyy-mm-dd hh:mi:ss(24小时制)

    -------------------------------------------------------------------------------------------------

    - | 21 or 121 | yyyy-mm-dd hh:mi:ss:mmm(24小时制)

例如当前时间为;2005-9-12 13:20:00

我要取其中的;2005-9-12

select convert(char(10),'2005-9-12 13:20:00',120)

CAST ( expression AS data_type )

    将某种数据类型的表达式显式转换为另一种数据类型

    declare @a int

    cast(@a as varchar(10))--从而连接动态语句

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