SQL SERVER中强制类型转换cast和convert的区别详解

SQL SERVER中强制类型转换cast和convert的区别

在SQL SERVER中,cast和convert函数都可用于类型转换,其功能是相同的,

只是语法不同.

cast一般更容易使用,convert的优点是可以格式化日期和数值.

select CAST('123' as int)  -- 123select CONVERT(int, '123') -- 123select CAST(123.4 as int)  -- 123select CONVERT(int, 123.4) -- 123 select CAST('123.4' as int)select CONVERT(int, '123.4')-- Conversion failed when converting the varchar value '123.4' to data type int.select CAST('123.4' as decimal) -- 123select CONVERT(decimal, '123.4') -- 123 select CAST('123.4' as decimal(9,2)) -- 123.40select CONVERT(decimal(9,2), '123.4') -- 123.40declare @Num moneyset @Num = 1234.56select CONVERT(varchar(20), @Num, 0) -- 1234.56select CONVERT(varchar(20), @Num, 1) -- 1,234.56select CONVERT(varchar(20), @Num, 2) -- 1234.5600

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