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.

代码

select CAST('' as int)   --

select CONVERT(int, '')  --

select CAST(123.4 as int)   --

select 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)  --

select CONVERT(decimal, '123.4') -- 123

select CAST('123.4' as decimal(9,2))  -- 123.40

select CONVERT(decimal(9,2), '123.4') -- 123.40

declare @Num money

set @Num = 1234.56

select CONVERT(varchar(20), @Num, 0)  -- 1234.56

select CONVERT(varchar(20), @Num, 1)  -- 1,234.56

select CONVERT(varchar(20), @Num, 2)  -- 1234.5600