create or replace function timecoverbegin(outbegintime   IN DATE,
                                          outendtime     IN DATE,
                                          inbegintime    IN DATE,
                                          inendtime      IN DATE)
   RETURN date
   as
   tempTbl varchar2(300);
   result date;
   begin
    tempTbl:=' create global temporary table tempTbl         
           (
             tempdate date
           ) on commit  delete  rows ';
   EXECUTE   IMMEDIATE tempTbl;
    insert into tempTbl(tempdate) values(outbegintime);
    insert into tempTbl(tempdate) values(outendtime);
    insert into tempTbl(tempdate) values(inbegintime);
    insert into tempTbl(tempdate) values(inendtime);
    select tempdate into result  from tempTbl order by tempdate;
    return result;
   end timecoverbegin
   ;
/