Date update problem

I also see a typo: you said the "day" column is named ATT_DAY but in your code you have ATT_DAT. Is that a typo in your posting here, or do you have the same in your actual code? Obviously that would make it "not work".

And you will sooner or later run into it again. Storing day parts as separate columns is bad design. Storing them as strings and not as numbers makes it even worse. But if you must store day parts as separate columns youc, at least, need to add check constraint. Otherwise:

create table tbl(
                 att_day   varchar2(2),
                 att_month varchar2(2),
                 att_year  varchar2(5)
                )
/
insert
  into tbl values(
                  'x',
                  'y',
                  'z'
                 )
/

1 row created.

SQL> insert
  into tbl values(
                  '29',
                  '2',
                  '2022'
                 )
/

1 row created.

SQL> rollback
  2  /

Rollback complete.

SQL>

As you can see we just inserted logically corrupt data. Check constraint would prevent that:

alter table tbl
  add constraint tbl_chk1
    check(to_date(att_day || '/' || att_month || '/' || att_year,'dd/mm/yyyy') <= date '9999-12-31')
/


Table altered.


SQL> insert
  2    into tbl values(
  3                    'x',
  4                    'y',
  5                    'z'
  6                   )
  7  /
                  'x',
                  *
ERROR at line 3:
ORA-01858: a non-numeric character was found where a numeric was expected

SQL> insert
  2    into tbl values(
  3                    '29',
  4                    '2',
  5                    '2022'
  6                   )
  7  /
                  '29',
                  *
ERROR at line 3:
ORA-01839: date not valid for month specified

SQL> insert
  2    into tbl values(
  3                    '28',
  4                    '2',
  5                    '2022'
  6                   )
  7  /

1 row created.

SQL>

SY.