Simple date format update/cleansing not working

Question

Dear All,
Some rows are not being updated after update
create table X(
Surname varchar2(20),
dob varchar2(20),
dobupdate varchar2(20));
insert into X values('Hookman','22-Apr-78','22-Apr-78');
insert into X values('Beverly','21/06/1966','21/06/1966');
insert into X values('Wickham','01/23/1985','01/23/1985');
insert into X values('Logmann','26/Dec/1972','26/Dec/1972');
insert into X values('Scooby','30.04.1966','30.04.1966');
insert into X values('Trumph','15-August-1967','15-August-1967');
insert into X values('Delaware','Aug-03-1961','Aug-03-1961');
insert into X values('Wicked','03.Sep.1961','03.Sep.1961');
insert into X values('Orlando','18.September.1961','18.September.1961');
SURNAME DOB DOBUPDATE
Hookman 22-Apr-78 22-Apr-78
Beverly 21/06/1966 21/06/1966
Wickham 01/23/1985 01/23/1985
Logmann 26/Dec/1972 26-DEC-1972
Scooby 30.04.1966 30-APR-1966
Trumph 15-August-1967 15-August-1967
Delaware Aug-03-1961 03-AUG-1961
Wicked 03.Sep.1961 03-SEP-1961
Orlando 18.September.1961 18.September.1961
9 rows selected.
=====================================
--Code below is meant to update person Beverly
Update x set dobupdate = to_char(to_date(dobupdate,'DD/MM/YYYY'),'DD-MON-YYYY')
where dobupdate like '__/__/____';
error - not valid month
=======================================================
--Code below is meant to update person  Trumph
Update x set dobupdate = to_char(to_date(dobupdate,'DD-MONTH-YYYY'),'DD-MON-YYYY')
where dobupdate like '__-_____-____';
0 row/s updated
=========================================================
--Code below is meant to update person Orlando
Update x set dobupdate = to_char(to_date(dobupdate,'DD.MMMM.YYYY'),'DD-MON-YYYY')
where dobupdate like '__._____.____';
0 row/s updated
Where am I going wrong. I hvae no problems with updating other records in the table except fot just these three patterns.
Help please.
Cube60

Answer 1

Thanks Warren, both suggested codes did not work and I can see why now. Alex has pointed it out.
Alex brought me to realise Wickham's DOB is in the American format. The update query could not resolve that format and how to update it but at least it could have updated that of Beverly and left that of Wickham.
After deleting Wickham completely, the update query worked on Beverly.
Am just doing some data cleansing from a poorly designed Access database now meant for Oracle.
So nothing can be done to resolve such mixture of date formats, I mean Uk and American.
But now, Why are the update statement below coming with 0 records updated.
The dates to be update are written like this 15-August-1967 and 18.September.1961 respectively
--Code below is meant to update person Trump
Update x set dobupdate = to_char(to_date(dobupdate,'DD-MM-YYYY'),'DD-MON-YYYY')
where dobupdate like '__-__-____';
0 row/s updated
=========================================================
--Code below is meant to update person Orlando
Update x set dobupdate = to_char(to_date(dobupdate,'DD.MMMM.YYYY'),'DD-MON-YYYY')
where dobupdate like '__._____.____';
0 row/s updated
many thanks
cube60
Message was edited by:
cube60