PL/SQL: ORA-30485: missing ORDER BY expression in the window specification
<p>I am compiling this Function but getting ERROR : missing ORDER BY expression in the window specification</p>

<pre><code>  CREATE OR REPLACE FUNCTION  WFir_get_act_section_cd(firnum IN NUMBER,langcd IN NUMBER) RETURN VARCHAR2 
               as
          ACTSEC  VARCHAR2(1500);
                 BEGIN
                  begin
  --- ERROR START                       
 select ltrim(max(sys_connect_by_path(NVL(act_long,' ') || '/' || NVL(section,' '),',')),',') as FIR_ACT_SEC into ACTSEC from(select NVL(act_long,' ') || '/' || NVL(section,' '), row_number() over() rn from rep_fir_sections sec
                         INNER JOIN m_act a on sec.act_cd = a.act_cd
                         INNER JOIN m_section c on sec.section_cd = c.section_code
                         and FIR_REG_NUM = FIRNum
                         and a.lang_cd = langcd)   WHERE ROWNUM &lt;=1 start with rn = 1
                      connect by prior rn = rn -1;
                      EXCEPTION
                      WHEN NO_DATA_FOUND THEN
                         NULL;
                   end;
                   return ACTSEC;
                END;
</code></pre>

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<p>When we are compiling above function after migrate this function form MYSQL to Oracle i am getting error "missing ORDER BY expression in the window specification" </p>

<p>I don't know why i am getting this ERROR, Please help me to resolve this ERROR </p>