Come utilizzare XPath con una variabile in Oracle XMLTable?

Puoi passare le variabili, basta definirle nella tua clausola di passaggio:

with table1 AS
  (select xmltype(
  '<abc>
     <def>
        <contract>1</contract>
        <oper>SFO</oper>
        <lmt>limit1</lmt>
     </def>
    <def>
       <contract>2</contract>
       <oper>boston</oper>
       <lmt >limit2</lmt>
    </def>
 </abc>'
 ) xmlcol from dual
 )
 SELECT u.*
   FROM table1
   ,    XMLTable('/abc/def[contract = $count]'
                 PASSING xmlcol, 1 as "count"
                 COLUMNS contract integer path 'contract',
                         oper     VARCHAR2(20) PATH 'oper' ) u 

  CONTRACT OPER               
---------- --------------------
         1 SFO