concat only if column value does not contain any specific prefix

I want to add the prefix to column’s data those who not like if the column’s value is 123,OI:909, 456,OI:789 then it updates to OI:123,OI:909, OI:456, OI:789

I tried following SQL

select col_1(case when col_1 NOT LIKE '%OI:%' then concat("OI:",col_1) end) from table_1;

Answer

You could try this syntax:

    select 
      case when col_1 NOT LIKE '%OI:%' 
        then concat("OI:",col_1) 
        ELSE col_1
      end   col1
      from table_1;