Oracle多个XMLAgg

Question

我正在用Oracle 10g构建一个sql查询， 并希望以xml格式获得sql输出：

<Users>
        <User>
            <USRID>1234</USRID>
            <USERNAME>ABCD</USERNAME>
            <ROLES>
                <ROLE>
                    <ROLEID>1</ROLEID>
                    <ROLENAME>GlobalAdministrator</ROLENAME>
                    <ISDEFAULTROLE>1</ISDEFAULTROLE>
                </ROLE>
                <ROLE>
                    <ROLEID>2</ROLEID>
                    <ROLENAME>Administrator</ROLENAME>
                    <ISDEFAULTROLE>0</ISDEFAULTROLE>
                </ROLE>
            </ROLES>
        </User>
        <User>
            <USRID>2312</USRID>
            <USERNAME>XUX</USERNAME>
            <ROLES>
                <ROLE>
                    <ROLEID>3</ROLEID>
                    <ROLENAME>AccountManager</ROLENAME>
                    <ISDEFAULTROLE>1</ISDEFAULTROLE>
                </ROLE>
                <ROLE>
                    <ROLEID>5</ROLEID>
                    <ROLENAME>Approver</ROLENAME>
                    <ISDEFAULTROLE>0</ISDEFAULTROLE>
                </ROLE>
            </ROLES>
        </User>
    </Users>

我刚刚构建的SQL：

SELECT XMLElement("Users", 
  XMLAgg(XMLElement("User",
    XMLElement("USRID",u.USRID) ,
    XMLElement("USERNAME",u.USERNAME) ,
    XMLElement("Roles",
      SELECT xmlagg(XMLElement("Role",
        XMLElement("ROLEID",ur.ROLEID),
        XMLElement("ROLENAME",r.NAME),
        xmlelement("ISDEFAULTROLE",ur.PRIMARY))
          FROM USERROLE ur,role r WHERE u.USRID = ur.USRID AND r.ROLEID  = ur.ROLEID))))).getClobVal()
FROM usr u

但它给出了以下错误： ORA-00936：缺少表达 00936. 00000 - “缺少表达” *原因：
*行动： 行错误：26列：1

我该怎么做？

Answer 1

我已经弄明白了：

SELECT XMLElement("Users",            
XMLAgg(XMLElement("User"                        
,XMLElement("USRID",u.USRID)                    
,XMLElement("USERNAME",u.USERNAME)
,xmlElement("Roles",
                 (
                   select xmlAgg(xmlElement("Role"
,XMLElement("ROLEID",ur.ROLEID)
,XMLElement("ROLENAME",r.NAME)
,xmlelement("ISDEFAULTROLE",ur.PRIMARY)))
from USERROLE ur,role r where u.USRID = ur.USRID and r.ROLEID = ur.ROLEID)
)))).getClobVal()
from usr u