Question : mysql UPDATE TABLE where field 1 IN feild 2

In my version of plain english, i have 2 things i need to do.

1)

I want to update MYTABLE
to remove what is contained in FIELDB from FIELDA

EG I HAVE THIS

FIELDA     FIELDB
hello1234   1234


I NEED THIS

FIELDA     FIELDB
hello          1234


PART 2)
I also need to know how to strip it out if it is in the MIDDLE of a field


FIELD_X           FIELD_Y
hello1234hello   1234


I NEED THIS

FIELD_X            FIELD_Y
hellohello            1234


Thankyou.

Answer : mysql UPDATE TABLE where field 1 IN feild 2

Below should work for both the cases:

update yourtable  set FIELDA=replace(FIELDA ,FIELDB,'');

Make sure you backup your table before trying any query.