SQL Server Performance Forum – Threads Archive

user-defined datatypes

I was wondering why I can’t use a user-defined datatype in the CAST() or CONVERT() functions, if anyone knows.

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By default UDFs cannot be used in CAST & CONVERT. Being UDFs are system based ones you have to use system data_types. Satya SKJ

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Maybe I’m getting my terminology mixed up…isn’t UDF a function? I was talking about datatypes. For example, if I created a datatype called "typeDateString", such as: sp_addtype typeDateString, ‘VARCHAR(11)’, NOT NULL Why can’t I use that in convert: CONVERT(typeDateString, GETDATE(), 101) Is there a way around this? Or am I just being lazy?

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Instead use VARCHAR directly in CONVERT function, by design User defined datatypes are not allowed. Satya SKJ –Apologies for mentioning UDFs read as user defined datatypes on previous post.

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