Oracle 18c

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select * from V$VERSION;


BANNER
BANNER_FULL
BANNER_LEGACY
CON_ID


Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
Version 18.4.0.0.0
Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
0


create table t23 (id number primary key, col1 varchar2(32), col2 varchar2(32))
/
create or replace trigger trg23 before update on t23 for each row
begin
  if :old.col1 <> :new.col1 then
    raise_application_error(-20000, 'You cannot change COL1!');
  end if;
end;
/
insert into t23 values (1, 'OLD', 'OLD')
/
1 rows affected

update t23 set col2 = 'NEW' where id = 1
/
1 rows affected

select * from t23
/


ID
COL1
COL2


1
OLD
NEW


update t23 set col1 = 'NEW' where id = 1
/
ORA-20000: You cannot change COL1!
ORA-06512: at "FIDDLE_VJLFMIRVTLNGURLSEUPK.TRG23", line 3
ORA-04088: error during execution of trigger 'FIDDLE_VJLFMIRVTLNGURLSEUPK.TRG23'

select * from t23
/


ID
COL1
COL2


1
OLD
NEW


create or replace trigger trg23 before update of col1 on t23 for each row
begin
  raise_application_error(-20001, 'You really cannot change COL1!');
end;
/
update t23 set col1 = 'NEW', col2 = 'SUPER NEW' where id = 1
/
ORA-20001: You really cannot change COL1!
ORA-06512: at "FIDDLE_VJLFMIRVTLNGURLSEUPK.TRG23", line 2
ORA-04088: error during execution of trigger 'FIDDLE_VJLFMIRVTLNGURLSEUPK.TRG23'

update t23 set col2 = 'SUPER NEW' where id = 1
/
1 rows affected

select * from t23
/


ID
COL1
COL2


1
OLD
SUPER NEW


create or replace trigger trg23 before update on t23 for each row
begin
  :new.col1 := :old.col1;
end;
/
update t23 set col1 = 'NEW' where id = 1
/
1 rows affected

select * from t23
/


ID
COL1
COL2


1
OLD
SUPER NEW