如果不为空，则在 XML 输出中包含字段，为空时省略

Question

我在这里的第一个问题，但我已经从这个伟大的网站阅读和学习了很多东西。 简短的介绍，我是一家全球公司的应用程序支持专家。 11 月开始，但已经忙于工作。

目前我正在从我们的 SQL Server 环境创建 XML 文件，以便向匈牙利海关申报我们的货物。在 Stackoverflow 线程的帮助下，一切都已经很好了。 现在我正在执行微调任务，并且正在努力解决以下问题。

在 XML 中有一些可选字段，有时需要填写，但并非总是如此。麻烦的是，当字段为空时，XML 将失败。因此，当为空时，不应包含完整的标签。并且当该字段被填充时，标签和数据应该包含在 XML 文件中。

示例；

 SELECT    [LocationName] as name
          ,[LocationPhone] as phone
          ,[LocationEmail] as email
          ,[LocationCountry] as country
          ,[LocationCity] as city
    FROM [XML_view]
    FOR XML PATH ('Location'), ELEMENTS, TYPE

姓名、国家和城市是必填项且始终填写，但电话和电子邮件可能为空，也可能不为空。

现在结果如下；

<Location 
  <name>BuildingOne</name>
  <phone />
  <email />
  <country>NL</country>
  <city>Amsterdam</city>
</Location>

但我希望电话和电子邮件在它们为空时不在 XML 中。

我尝试使用 IF EXISTS 和 IF NOT NULL，但这不起作用。 有人有什么建议吗？

Answer 1

我的猜测是你有空字符串而不是 NULL 值。这显示了差异；

;with cte as (
select 'John' as [LocationName], '0123456789' as [LocationPhone], 'john@smith.com' as [LocationEmail],'UK' as [LocationCountry],'London' as [LocationCity]
union all
select 'Peter' as [LocationName], '' as [LocationPhone], '' as [LocationEmail],'UK' as [LocationCountry],'Sheffield' as [LocationCity]
union all
select 'Sally' as [LocationName], null as [LocationPhone], null as [LocationEmail],'UK' as [LocationCountry],'Reading' as [LocationCity]
)
 SELECT    [LocationName] as name
          ,[LocationPhone] as phone
          ,[LocationEmail] as email
          ,[LocationCountry] as country
          ,[LocationCity] as city
    FROM cte
    FOR XML PATH ('Location'), ELEMENTS, TYPE

您可以使用NULLIF 将空字符串更改为NULL，它们将从XML 中消失；

;with cte as (
select 'John' as [LocationName], '0123456789' as [LocationPhone], 'john@smith.com' as [LocationEmail],'UK' as [LocationCountry],'London' as [LocationCity]
union all
select 'Peter' as [LocationName], '' as [LocationPhone], '' as [LocationEmail],'UK' as [LocationCountry],'Sheffield' as [LocationCity]
union all
select 'Sally' as [LocationName], null as [LocationPhone], null as [LocationEmail],'UK' as [LocationCountry],'Reading' as [LocationCity]
)
 SELECT    nullif([LocationName], '') as name
          ,nullif([LocationPhone], '') as phone
          ,nullif([LocationEmail], '') as email
          ,nullif([LocationCountry], '') as country
          ,nullif([LocationCity], '') as city
    FROM cte
    FOR XML PATH ('Location'), ELEMENTS, TYPE