If you are just looking to trim an entry then you can use string functions to quickly remove part of an entry.
If you are looking for something more complex (like changing the name of a company or altering links inside text) then you may need to use Pattern matching (LIKE or regular expressions) and pos. some processing before updating the specific entry.
It depends on how complex your data and requirements are.
(Please note: While like is reasonably fast, a regular expression match will usually slow down your server quite a bit).
