使用 SQL 服务器 2016 解析 XML

Question

I'm trying to clean up some SQL code. Currently I have an XML like:

DECLARE @xml xml = N'<PubmedArticleSet>
  <PubmedArticle>
    <MedlineCitation Status="MEDLINE" Owner="NLM">           
      <ArticleIdList>           
        <ArticleId IdType="pii">0092-8674(92)90516-F</ArticleId>
        <ArticleId IdType="pubmed">1423608</ArticleId>
        <ArticleId IdType="doi">10.1016/0092-8674(92)90516-f</ArticleId>
      </ArticleIdList>
    </PubmedData>
  </PubmedArticle>
</PubmedArticleSet>'

And I need to get the value of the ArticleId with the attribute of

    IdType ="pubmed"

I would like something like and XQUERY method that could:

DECLARE @PMID NVARCHAR(15)
SET @PMID =  @xml.value('(//PubmedData/ArticleIdList/ArticleId/@IdType)[1]', 'varchar(15)' ) 

But that pulls the IdType "pii" of the first node. And

SET @PMID =  @xml.value('(//PubmedData/ArticleIdList/ArticleId/@IdType = "pubmed")[1]', 'varchar(15)' ) 

Brings back true.

Is there a way to filter based upon "pubmed" and then get the number 1423608? So @PMID would then be equal to 1423608.

Answer 1

Your provided XML is not well-formed. There are several tags missing, hope this is corrected here:

DECLARE @xml xml = N'<PubmedArticleSet>
  <PubmedArticle>
  <PubmedData>
    <MedlineCitation Status="MEDLINE" Owner="NLM">           
      <ArticleIdList>           
        <ArticleId IdType="pii">0092-8674(92)90516-F</ArticleId>
        <ArticleId IdType="pubmed">1423608</ArticleId>
        <ArticleId IdType="doi">10.1016/0092-8674(92)90516-f</ArticleId>
      </ArticleIdList>
      </MedlineCitation>
    </PubmedData>
  </PubmedArticle>
</PubmedArticleSet>';

DECLARE @IdToFind VARCHAR(100)='pubmed';

SELECT @xml.value('(/PubmedArticleSet
                    /PubmedArticle
                    /PubmedData
                    /MedlineCitation
                    /ArticleIdList
                    /ArticleId[@IdType=sql:variable("@IdToFind")]
                    /text())[1]','int');

The idea in short:

• We can use variable to get this a bit more generic.
• We dive into the XML, down to the <ArticleIdList> and
• find the one <ArticleId> where the attribute IdType equals the given value.
• From there we return the text() .

You would get the same with a simple deep search too:

SELECT @xml.value('(//ArticleId[@IdType=sql:variable("@IdToFind")]/text())[1]','int');

But the general advise is: Be as specific as possible.