oracle 10g using update and concat

Question

My table structure is this.

gno  gdate             DCNo    DCDATE 
g/1  11/12/2018        cnt/1   12/12/2018
g/2  20/12/2018        cnt/2   13/12/2018
g/3  11/12/2018         3      11/12/2018
g/4  10/12/2018         4      10/12/2018 

I want to update all columns in dcno with cnt/no. here row 3 and 4 have to be updated to cnt/3 and cnt/4

Answer 1

Is this what you want?

update t
    set DCNO = 'cnt/' || DCNO
    where DCNO not like 'cnt/%';

Answer 2

Try this

update tablename set dcno='cnt/'||dcno
where dcnot not like 'cnt/%'

Answer 3

use case

update table
set DCNo= case when DCNo in ('3','4')then 'cnt/'||DCNO end