Question

Table before solve:

       ID NAME             DATA




     1 zhang               9
     1 zhang              12
     2 wang                1
     2 wang                2

/this is the table before solved/
Table after solve:
    ID NAME             DATA


     1 DIY                13
     2 DIY                 3

/this is what I want to get result/

There is the procedure:

update A a 
set a.date=(select  max(f_get(f.id,f.date,g.date))
           from A f,A g 
            where f.date!=g.date 
            and f.id=a.id);


--function f_get()
create or replace function f_get
      (id in varchar2,date in varchar,date2 in varchar ) 
    return varchar is
  Result varchar     
      date3 varchar(4);

begin

      select nvl(date,date2) into date3 
      from dual;

      Result:=date3;

    delete  from A a 
    where a.ID=id  
    and a.date=date2;--there is error 

  return(Result);
end  f_get;

												

Answer 1

Your question does its best to hide itself, but this is the point:

“–there is error “

The error you get is (presumably) ORA-14551: cannot perform a DML operation inside a query, which you are getting because you are calling a FUNCTION which includes a DELETE command from a SELECT statement.

Oracle’s transactional model doesn’t allow queries to change the state of the database. Instead of a FUNCTION you need to write a procedure.

Although, if you want to remove duplicate rows, a straight SQL solution will suffice. Something like

delete from a
where (id, date) not in 
    ( select id, max(date) from a
      group by id)
/