Calling PLSQL from DML Statements

Question

hello everybody,
i have just a minor "problem". (this confuses me because of the 1z0-147 programming plsql exam)
Oracle Documentation (10G R2 Application Developer's Guide - Fundamentals - 7 Coding PL/SQL Procedures and Packages) says:
The following restrictions are enforced on subprograms:
=> A subprogram called from a DML statement may not read or modify the particular table being modified by that DML statement.
i did some tests but they resulted not in an error (mutating table exception or whatever); so maybe Oracle's documentation is inaccurate here ?
here is an example which works fine (10G R2):
drop table ttestuh
create table ttestuh ( s varchar2(19));
insert into ttestuh values ( 'Oracle' );
create or replace function getVal return varchar2 is
retval ttestuh.s%type;
begin
select s into retval from ttestuh where rownum <2;
return retval;
end;
create or replace function getVal2 return varchar2 is
begin
insert into ttestuh values ( 'ASDF');
return 'ASDF';
end;
insert into ttestuh values ( getval );
insert into ttestuh values ( getval2 );
commit
select * from ttestuh
rows:
Oracle
Oracle
ASDF
ASDFit seems to be that even DML-doing PLSQL calls are allowed when called from an insert statement on the same table.
(for update statements an mutating table exception is raised)
thanks in advance for your opinions
ulli

Answer 1

I believe what docs are saying is correct. And also what you are seeing is correct. There may be a small issue in understanding the impact.
SQL>  create or replace function fun1
  2   return number
  3   is
  4   begin
  5   delete test;
  6   end;
  7  .
SQL>  create or replace function fun1
  2   return number
  3   is
  4   begin
  5   update test set owner='amn';
  6  end;
  7  /
Function created.
SQL> select fun1 from test;
select fun1 from test
ERROR at line 1:
ORA-14551: cannot perform a DML operation inside a query
ORA-06512: at "AMAN.FUN1", line 5
SQL>  create or replace function fun1
  2   return number
  3   is
  4   begin
  5  insert into test(owner) values('new');
  6  end;
  7  /
Function created.
SQL> select fun1 from test;
select fun1 from test
ERROR at line 1:
ORA-14551: cannot perform a DML operation inside a query
ORA-06512: at "AMAN.FUN1", line 5
SQL>The mutating error means that the data that you are trying to change is also read by the same session and this means, Oralce can't give a "dirty read" to you. That's why in the case of Update, the mutating error is returned. The insert statement is inserting new data which anyways your select can't see as long as its not committed and with it you haven't changed the existing one that's why its allowed.
SQL> create or replace function fun1
  2  return varchar2
  3  is
  4  a varchar2(10);
  5  begin
  6  select owner into a from test where rownum<=1;
  7  end;
  8  /
Function created.
SQL> update test owner=fun1;
update test owner=fun1
ERROR at line 1:
ORA-00971: missing SET keyword
SQL> update test set owner=fun1;
update test set owner=fun1
ERROR at line 1:
ORA-04091: table AMAN.TEST is mutating, trigger/function may not see it
ORA-06512: at "AMAN.FUN1", line 6
SQL>HTH
Aman....