Convert oracle vatchar2 to clob method

create table cssc_result1  as select * from cssc_result where 1=2;

alter table cssc_result1 modify (DEFECT_NAME clob);

alter table cssc_result1 modify (DEFECT_REASON clob);

insert into cssc_result1 select * from cssc_result;

drop table cssc_result;

rename cssc_result1 to cssc_result;