存在数据的oracle中修改varchar2数据类型为date

//把varchar2类型数据转换为date

alter table test add datetime date;//添加一个字段类型为date

comment on column test.datetime is '备注';//加备注
update test set datetime = TO_DATE(daad,'yyyymmddhh24miss')//把原来的数据转化为date并复制过来
alter table test drop column daad; //删除原字段
commit;

//把varchar2类型数据转换为number

alter table test add numb number;
 update test set numb = to_number(SASA);
 alter table test drop column SASA;
 COMMIT;