问题
I have a function that takes a number as an input and converts it to a date. This number isn't any standard form of date number, so I have to manually subdivide portions of the number to various date parts, cast the date parts to varchar strings and then, concatenate and cast the strings to a new datetime object.
My question is how can I catch a casting failure and return a null or low-range value from my function? I would prefer for my function to "passively" fail, returning a default value, instead of returning a fail code to my stored procedure. TRY/CATCH statements apparently don't work form within functions (unless there is some type of definition flag that I am unaware of) and trying the standard '@@Error <> 0' method doesn't work either.
回答1:
Incidentally this sounds like it could be a scalar UDF. This is a performance disaster, as Alex's blog points out. http://sqlblog.com/blogs/alexander_kuznetsov/archive/2008/05/23/reuse-your-code-with-cross-apply.aspx
回答2:
SELECT CASE WHEN ISDATE(@yourParameter) = 1
THEN CAST(@yourParameter AS DATETIME)
ELSE YourDefaultValue
END
回答3:
Since the format is nonstandard it sounds to me like you are stuck with doing all the validation yourself, prior to casting. Making sure that the individual pieces are numeric, checking that the month is between 1 and 12, making sure it's not Feb 30, etc. If anything fails you return nothing.
来源：https://stackoverflow.com/questions/5353796/catching-errors-from-within-a-user-defined-function-in-sql-server-2005