Convert has a third parameter that is optional and is called style. It is mostly used with dates. For example check out the next script:

declare @dt char(10)

select @dt = '31/01/2010'

--This will always work

select convert(smalldatetime, @dt, 103)

--This might work and might fail

select cast (@dt as smalldatetime)

go

declare @dt char(10)

select @dt = '01/31/2010'

--This will always work

select convert(smalldatetime, @dt, 101)

--This might work and might fail

select cast (@dt as smalldatetime)

Notice that with the convert function, I was able to work with the string as date regardless of the format that I was using because of the third parameter, but when I used cast function only one format could be cast to smalldatetime.

Adi