create or replace function F_TbUserInfo_GetDept(
  V_Dept_Id int, 
  V_Usr_Id int, 
  V_SearchField varchar2
) return varchar2
is
  v_list varchar2(2000):='';
begin
  for rec in (
    select decode(V_SearchField,'ID',ltrim(str(Dept_Id)),Dept_Name end+',') CNAME 
    from TbDeptInfo a,TbDeptUser b where b.DuDept_Id=a.Dept_Id and dept_state=1 
    and ( V_Dept_Id=-1 or Dept_Id=V_Dept_Id ) 
    and ( V_Usr_Id=-1 or b.DuUsr_Id=V_Usr_Id )
  )
  loop
    v_list := v_list|| REC.CNAME;
  end loop;
  IF LENGTH(V_LIST)>0 THEN
    V_LIST := SUBSTR(V_LIST,1,LENGTH(V_LIST)-1);
  END IF;
  return v_list;
end;
/

------解决方案--------------------
主要是：
去掉变量前的@
等号从＝ 到 :＝

------解决方案--------------------
CREATE OR REPLACE FUNCTION F_TbUserInfo_GetDept
(
 v_Dept_Id IN NUMBER,
 v_Usr_Id IN NUMBER,
 v_SearchField IN VARCHAR2
)
RETURN VARCHAR2
AS
  v_List VARCHAR2(2000);
BEGIN
  v_List := '';

  SELECT v_List || CASE
                        WHEN v_SearchField = 'Id' THEN LTRIM(sqlserver_utilities.str(Dept_Id))
         ELSE Dept_Name
            END || ','
    INTO v_List
    FROM TbDeptInfo a,
         TbDeptUser b
     WHERE b.DuDept_Id = a.Dept_Id
             AND dept_state = 1
             AND ( v_Dept_Id = -1
             OR Dept_Id = v_Dept_Id )
             AND ( v_Usr_Id = -1
             OR b.DuUsr_Id = v_Usr_Id );

  IF ( LENGTH(v_List) > 0 ) THEN
     v_List := SUBSTR(v_List, 0, LENGTH(v_List) - 1);

  END IF;

  RETURN v_List;

END;