title: single-row subquery returns more than one row - how to find the duplicate?
body: <p>iam not a big ORACLE - SQL Expert, so i hope someone knows a good way to find the "duplicate" record wich is causing the: <strong>single-row subquery returns more than one row</strong> error.</p>
  
  <p>This my Statement:</p>
  
  <pre><code>    SELECT
      CAST(af.SAP_SID AS VARCHAR2(4000)) APP_ID,
      (SELECT DR_OPTION
         FROM
            DR_OPTIONS 
         WHERE DR_OPTIONS.ID = (
              select dr_option from applications where applications.sap_sid = af.sap_sid)) DR_OPTION
  FROM
      APPLICATIONS_FILER_VIEW af
  </code></pre>
  
  <p>it works on my test system, so iam "sure" there must be an error inside the available data records, but i have no idea how to find those .. </p>