SqlServer基础：类型转换Cast和Convert-Mysql Tutorial-php.cn

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SqlServer基础：类型转换Cast和Convert

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Jun 07, 2016 pm 03:24 PM

sqlserverBasetypeConvert

在SqlServer要对不同类型的数据进行运算时，需要将其转换为相同类型之后再做操作，而SqlServer中有两个函数可以进行数据转换，即：Cast和Convert 1、Cast CAST(expression AS data_type[(length)]),其中expression为任何有效的表达式；data_type为要

在SqlServer要对不同类型的数据进行运算时，需要将其转换为相同类型之后再做操作，而SqlServer中有两个函数可以进行数据转换，即：Cast和Convert

1、Cast

　　CAST(expression AS data_type[(length)]),其中expression为任何有效的表达式；data_type为要转换的数据类型；length为数据类型的长度，是可选参数，因为有些数据类型是没有长度的。举例：CAST(Nid AS varchar(50))或CAST(Name AS int)

2、Convert

　　CONVERT(data_type [(length)],expression [,style]),其中data_type为要转换的数据类型；length为数据类型的长度(可选)；expression为任何有效的表达式；style是样式；此函数一般用于将datetime和smalldatetime数据转换为字符数据(nchar,nvarchar,char,varchar,nchar或nvarchar数据类型)的日期格式的样式，或者用于将float，real，money或smallmoney数据转换为字符数据(nchar,nvarchar,char,varchar,)的字符串格式的样式，如果style为null，则返回的结果也为null。对于样式来说，有一个样式表，其中的样式代号1，2，3，4或101，102，103代表着一种特定的格式。
举例：CONVERT(varchar(20),PublishDate,1)，其中varchar的长度也可以控制时间格式的长度。
　　 CONVERT(char(20),operationTime,120)

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