SQL> drop table tableone
  2  /

Table dropped.

SQL> 
SQL> create table tableone
  2  (
  3   keyid varchar2(10)
  4  ,col1 varchar2(10)
  5  ,col2 varchar2(10)
  6  )
  7  /

Table created.

SQL> 
SQL> insert into tableone values ('KEYONE','THREE','FOUR');

1 row created.

SQL> commit;

Commit complete.

SQL> 
SQL> select * from tableone;

KEYID      COL1       COL2
---------- ---------- ----------
KEYONE     THREE      FOUR

SQL> 
SQL> create or replace trigger aur_tableone
  2  after update on tableone
  3  for each row
  4  declare
  5     r1 tableone%rowtype;
  6  begin
  7     select *
  8     into r1
  9     from tableone
 10     where keyid = :new.keyid;
 11  raise_application_error(-20999,'(keyid,col1,col2)=('||r1.keyid||','||r1.col1||','||r1.col2||')');
 12  end;
 13  /

Trigger created.

SQL> 
SQL> Update tableone Set COL1 = 'FOUR', COL2 = 'FIVE' Where KEYID = 'KEYONE';
Update tableone Set COL1 = 'FOUR', COL2 = 'FIVE' Where KEYID = 'KEYONE'
       *
ERROR at line 1:
ORA-04091: table KEVIN.TABLEONE is mutating, trigger/function may not see it
ORA-06512: at "KEVIN.AUR_TABLEONE", line 4
ORA-04088: error during execution of trigger 'KEVIN.AUR_TABLEONE'


SQL> 
SQL> create or replace trigger aur_tableone
  2  after update on tableone
  3  for each row
  4  declare
  5     pragma autonomous_transaction;
  6     r1 tableone%rowtype;
  7  begin
  8     select *
  9     into r1
 10     from tableone
 11     where keyid = :new.keyid;
 12  raise_application_error(-20999,'(keyid,col1,col2)=('||r1.keyid||','||r1.col1||','||r1.col2||')');
 13  end;
 14  /

Trigger created.

SQL> 
SQL> Update tableone Set COL1 = 'FOUR', COL2 = 'FIVE' Where KEYID = 'KEYONE';
Update tableone Set COL1 = 'FOUR', COL2 = 'FIVE' Where KEYID = 'KEYONE'
       *
ERROR at line 1:
ORA-20999: (keyid,col1,col2)=(KEYONE,THREE,FOUR)
ORA-06512: at "KEVIN.AUR_TABLEONE", line 9
ORA-04088: error during execution of trigger 'KEVIN.AUR_TABLEONE'


SQL>