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)  -- 123
select convert(int, '123') -- 123

select cast(123.4 as int)  -- 123
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) -- 123
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

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