Implementing User-Defined Function with expression

Question

Is it possible to implement user-defined function in SQL Server that has parameter expression and return type is same as expression?

Basically, I'm looking to implement extended version of NULLIF function.

You can use sql_variant, but otherwise I don't think you can have dynamic typing. — Gordon Linoff
– Gordon Linoff, Commented Dec 3, 2017 at 12:29
And sql_variant often doesn't really help as you need to cast it to the base type if you want to perform any further operations on it. — Martin Smith
– Martin Smith, Commented Dec 3, 2017 at 12:43

Martin Smith · Accepted Answer · 2017-12-03 12:40:35Z

1

No.

This is a capability that only built in functions have.

The grammar for creating scalar functions requires

RETURNS return_data_type

Which means you have to pick a specific return data type at design time. You can't have it inferred from the datatype passed in.

answered Dec 3, 2017 at 12:40

Martin Smith

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