将空列表传递给标量函数上的用户定义表类型参数 [英] Passing empty list to user defined table type parameter on a scalar function

问题描述

所以我有这个用户定义的表类型参数，它在我的标量函数中使用并且可能为空.我已阅读有关将空列表传递给存储过程上的表值参数的主题:绑定空列表或存储过程 (.net) 上表值参数的空值
基本上，正如其中一位回复者所说:

So I have this user-defined table type parameter, which is used in my scalar function and might be empty. I've read this topic about passing empty list to table-valued parameter on a stored procedure: Binding empty list or null value to table valued parameter on a stored procedure (.net)
And basically, as one of the repliers said:

"诀窍是:根本不传入参数.默认表值参数的值是一个空表"

"The trick is: don’t pass in the parameter at all. The default value for a table-valued parameter is an empty table"

但是，当我在标量函数上尝试此操作时，出现错误:

However, when I try this on scalar function, I get an error:

为过程提供的参数数量不足或功能

An insufficient number of arguments were supplied for the procedure or function

那么如何将空值传递给标量函数上的表值参数?

So how do I pass empty value to table-valued parameter on a scalar function?

推荐答案

函数的参数不是可选的，因此您需要将兼容的 TVP 传递给函数.我不确定我是否理解采用 TVP 类型但不需要的标量值函数的意义 - 这个函数有什么作用，没有 TVP 怎么办?你确定这不是 TVF?

Arguments to functions aren't optional, so you need to pass a compatible TVP to the function. I'm not sure I understand the point of a scalar-valued function that takes a TVP type but doesn't need to - what does this function do and how can it do it without the TVP? Are you sure this isn't meant to be a TVF?

无论如何，这是将空 TVP 传递给标量函数的方法:

Anyway here is how you can pass an empty TVP to a scalar function:

DECLARE @x dbo.TVP_type_name;
SELECT dbo.function_name(@x);

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