获取XML子节点的值与动态父在SQL Server

Question

我在SQL Server中的Process表是这样的：

workflowXML列有值是这样的：

<bpmn:definitions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
     xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL" 
     xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" 
     xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" 
     xmlns:di="http://www.omg.org/spec/DD/20100524/DI" 
     id="Definitions_1" targetNamespace="http://bpmn.io/schema/bpmn"> 
    <bpmn:process id="Process_1" isExecutable="false"> 
     <bpmn:startEvent id="StartEvent_1rin5au"> 
      <bpmn:outgoing>SequenceFlow_1q36672</bpmn:outgoing> 
     </bpmn:startEvent> 
     <bpmn:userTask id="UserTask_038517r" name="addRequest"> 
      <bpmn:incoming>SequenceFlow_1q36672</bpmn:incoming> 
      <bpmn:outgoing>SequenceFlow_0dpq0oe</bpmn:outgoing> 
     </bpmn:userTask>  
     <bpmn:serviceTask id="ServiceTask_17e1u09" name="checkRequest"> 
      <bpmn:incoming>SequenceFlow_1q36672</bpmn:incoming> 
      <bpmn:outgoing>SequenceFlow_1233bp0</bpmn:outgoing> 
     </bpmn:serviceTask>   
    </bpmn:process>  
</bpmn:definitions> 

我需要一个SQL查询得到的id节点的incoming的值与outgoing的值相等，即bpmn:startEvent节点。

我测试这个子查询：

;WITH XMLNAMESPACES('http://www.omg.org/spec/BPMN/20100524/MODEL' AS bpmn) 
select 
    p.workflowXML.value('(bpmn:definitions/bpmn:process/bpmn:userTask/bpmn:incoming)[1]', 'nvarchar(max)') 
from 
    Process as p  

但这个代码只返回结果为bpmn:userTask。我用其他的子查询：

;WITH XMLNAMESPACES('http://www.omg.org/spec/BPMN/20100524/MODEL' AS bpmn) 
select 
    p.workflowXML.value('(bpmn:definitions/bpmn:process/../bpmn:incoming)[1]', 'nvarchar(max)') 
from 
    Process as p 

但它返回null。

我的查询是这样的：

declare @SequenceFlow nvarchar(max) 
;WITH XMLNAMESPACES('http://www.omg.org/spec/BPMN/20100524/MODEL' AS bpmn) 
select @SequenceFlow = 
(
SELECT p.workflowXML.value('(/bpmn:definitions/bpmn:process/bpmn:startEvent/bpmn:outgoing)[1]','nvarchar(max)') 
from Process as p 
where ID = 1 
) 

;WITH XMLNAMESPACES('http://www.omg.org/spec/BPMN/20100524/MODEL' AS bpmn) 
select p.workflowXML.value('(bpmn:definitions/bpmn:process/../bpmn:incoming)[1]','nvarchar(max)') 
from Process as p 
where p.workflowXML.value('(bpmn:definitions/bpmn:process/../bpmn:incoming)[1]','nvarchar(max)') = @SequenceFlow 

这将是非常有益的，如果有人可以解释这个问题的解决方案。

谢谢。

Answer 1

您可以使用*引用任意名称的元素：

;WITH XMLNAMESPACES('http://www.omg.org/spec/BPMN/20100524/MODEL' AS bpmn) 
select t.c.value('@id','nvarchar(max)') 
from Process as p 
    cross apply p.DiagramXML.nodes('bpmn:definitions/bpmn:process/*') AS t(c) 
where t.c.value('bpmn:incoming[1]', 'nvarchar(max)') = @SequenceFlow 

注意cross apply用于在bpmn:process元素级别的子切碎XML数据。这允许查询从单个XML列数据返回多行。