oracle to the table field to replace VARCHAR2 CLOB

select * from TableName

- Add a field

alter table TableName add 字段2 clob;

- this field duplicated data
update TableName set field 2 = to_clob (Field);

- changed its name to the field

alter table TableName rename column field to field. 3;
alter table TableName rename column 2 field to field;

- annotated
. Comment on column TableName. 3 field is 'set forth Problems (20,190,907 day waste, into clob type)';
Comment ON the TableName column field is 'set forth Problems';.