Modify the field type of existing data in Oracle

Modify the field type of existing data in Oracle [SQL] www.2cto.com create table t_person (id varchar2 (200) primary key, name varchar2 (200), address varchar2 (200 )); [SQL] insert into t_person (id, name, address) values (sys_guid (), 'hangsan', 'beijing'); insert into t_person (id, name, address) values (sys_guid (), 'lisi', 'shangqiu '); change the varchar2 type of address to the clob type (1) [SQL] alter table t_person rename column address to myaddress; change the original field name and address to myaddress (2) [SQL] alter table t_person add address clob; add an original field name address in the table and define the type as the type you want to change. Here is clob (3) [SQL] update t_person set address = myaddress; add the backup myaddress field to the new field address (4) [SQL] alter table t_person drop column myaddress; Delete the backup field myaddress