Hoew to remove paticular string from the value in a filed?

[Veeru]

I have the Field with id

i want to  only  3 digits  id For example:
if i take t0123-123 here i want remove t0
t456-456 here i want remove t
t1023-023 here i want to remove t1
The excepted output as shown below:

ID	expected ID
a	a
t0123	123
t456	456
t1023	023

[diogofgm]

An option other than the one suggested by rrovers is to use the rex command:

| makeresults 
| eval id="a,t1023,t456,t0123"
| makemv delim="," id
| mvexpand id
| fields - _time
| rex field=id "(?<expected_id>\w{1,3}$)"

This option adds a bit more flexibility given that you can do some validation on the content by changing the regex (e.g. you want only the id's digits just swap \w with \d in the rex command) 

[rrovers]

| makeresults 
| eval ID="t1023" 
| eval IDlen=len(ID) 
| eval IDlen2=IDlen-2 
| eval IDtest=substr(ID,IDlen2) 
| table IDtest