varchar2转变为clog

1先备份数据表:

create table NEW_TABLE_NAME AS SELECT * FROM TABLE_NAME WHERE 1=1;

2清空原表内数据

TRUNCATE TABLE TABLE_NAME;

3变更数据类型

alter table TABLE_NAME modify column_a long;

alter table TABLE_NAME modify column_a clob;

4将备份中的数据插入回来

insert into TABLE_NAME select * from NEW_TABLE_NAME;