如要修改的字段为A,(我的版本是9i) alter table mytab add(a1 varchar2) update table mytab set a1=a alter table mytab drop column a alter table mytab rename column a1 to a
如果clob字段的最大length不大于4000的话,可以,否则丢数据的。 alter table t add colx varchar2(4000); update t set colx=dbms_lob.substr(clobCol,1,dbms_lob.getLength(clobCol)); alter table t drop COLUMN clobCol;
alter table table_name modify(colum_name,varchar2(4000))
alter table mytab add(a1 varchar2)
update table mytab set a1=a
alter table mytab drop column a
alter table mytab rename column a1 to a
alter table t add colx varchar2(4000);
update t set colx=dbms_lob.substr(clobCol,1,dbms_lob.getLength(clobCol));
alter table t drop COLUMN clobCol;