xquery - 如何检查 XQuery 函数中的空日期参数？

Question

考虑以下检查空日期的代码：

declare xqse function tns:isEmptyDate($dob as xs:date) as xs:boolean {
    if(empty($dob)) then {
    }
}

执行时，为什么会在 ALDSP 中出现以下错误：

weblogic.xml.query.exceptions.XQueryDynamicException: {err}XP0021: "": can not cast to {http://www.w3.org/2001/XMLSchema}date: error: date: Invalid date value: wrong type:

Answer 1

OK, I've had a look at this and I think you'll be able to run your query by defining your function as

declare function tns:isEmptyDate($dob as xs:date?) as xs:boolean

Note the ? after the type - it means that the argument may be the empty sequence.

I tested this out in Oxygen, using Saxon-B... sorry, I don't have access to the software you're using.

Here's my function definition.

declare function tns:isEmptyDate($dob as xs:date?) as xs:boolean {
    let $empty := if (empty($dob))
        then true()
        else false()
    return $empty
};

Running against this file:

<?xml version="1.0" encoding="UTF-8"?>
<datetime>2002-09-24</datetime>

returns true, and running against this file:

<?xml version="1.0" encoding="UTF-8"?>
<dontmatch>2002-09-24</dontmatch>

returns false.

Running the same function without the questionmark, on the second document, errors with:

Severity: error. Description: An empty sequence is not allowed as the first argument of tns:isEmptyDate()

Answer 2

在类型声明后用问号或星号试​​试这个。

例如，

$dob as xs:date 表示 $dob 是 1 个项目的序列（类型为 xs:date）

$dob 作为 xs:date? 表示 $dob 是 1 项或无项的序列（每个项的类型均为 xs:date）

$dob as xs:date* 意味着 $dob 是一个没有或多个项目的序列（每个项目都是 xs:date 类型）

Answer 3

使用函数empty()而不是编写自己的函数。如果序列的计数为零，则 Empty 将返回 true，其中xs:date?可以是长度为零或一的序列。

Answer 4

我只修改了 XQuery，但我怀疑正在生成错误，因为函数签名($dob as xs:date)需要日期类型，而您正在传递其他内容，例如空值。