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(),getdate(),) now

结果为

now

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//

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

style数字在转换时间时的含义如下

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

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- |  or  | mon dd yyyy hh:miAM(或PM)

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 |  | mm/dd/yy

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 |  | yy-mm-dd

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 |  | dd/mm/yy

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 |  | dd-mm-yy

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 |  | dd-mm-yy

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 |  | dd mon yy

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 |  | mon dd,yy

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 |  | hh:mm:ss

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

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 |  | mm-dd-yy

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

 |  | yy/mm/dd

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

 |  | yymmdd

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

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 |  | hh:mi:ss:mmm(24小时制)

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- |  or  | yyyy-mm-dd hh:mi:ss(24小时制)

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

例如当前时间为：-- ::

我要取其中的：--

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

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())--从而连接动态语句