sql - How to update Partial Value in Postgresql?

Question

I have a table like below...

value        Name
-------------------
Data-1      Aarong
Data-125    Aarong
INT-121     Aarong
INT-122     Aarong

I would like to update value column with existing value. After update value column like below.

value       Name
-------------------
D-1        Aarong
D-125      Aarong
I-121      Aarong
I-122      Aarong

Answer 1

If the string always contain just one dash, you could do this with split_part():

update mytable set value = 
    left(value, 1) || '-' || split_part(value, '-', 2)

if there may be more than one dash, and you want everything after the first:

update mytable set value = 
    left(value, 1) || substr(value, position('-' in value))

Demo on DB Fiddle