update shift_table

set shift = case shift_id

when 1 then 'C'

when 2 then 'B'

else shift_id

end

where shift_id < 3

You can expand and/or alter the CASE statement to your specific needs. Also try to get a generic alteration of the new value. Like for example: you could alter the above sample to update shift_table

set shift = char(ascii(shift)+1)

where shift_id < 3if you need to take the next character for every value. Then a CASE statement is not required anymore.