我现在已经使用一张表，现在已经不能再进行删除表操作，我想在这个表上加一个主关键字，有什么办法解决呀！各位大侠，请帮忙！

alter table sale add constraint Sale_pk primary key(sale_id) using index storage(initial 1M next 1M pctincrease 0) tablespace dw_idx21 unrecoverable;

要建的主关键字上有重复记录么？

1.
On the table you want to add primary key,
Alter table tname add constraints pk_tname primary key (col1) disable;
Here 'disable' ensures that the primary key constraint will be created but in a disable status. Thus no error will be reported on primary key conflict.
2.
run $oracle_home\rdbms\admin\utlexcpt.sql to create table 'exceptions'

3.
alter table tname enable primary key exceptions into exceptions
This will record all the conflict rows' rowid into table 'exceptions'
4.
select * from tname where rowid in (select row_id from exceptions)
This statement will return all the rows having conflict.

你的意思是不是在已有的表上增加一个新的字段，且这个字段作为这张表的主键。

对呀，我想以后每新增一条记录ORACLE系统给他赋一个主键值！
可以吗？谢谢！

1.
ALTER TABLE TNAME ADD (PK_NO NUMBER(20));
2.
UPDATE TNAME SET PK_NO = ROWNUM;
3.
ALTER TABLE TNAME ADD CONSTRAINTS PK_TNAME PRIMARY KEY (PK_NO);
4.
CREATE SEQUENCE SEQ_PK_NO;
5.
create or replace trigger t_pk_test
before insert on test
for each row
begin
   if ( :new.pk_no is null ) then
      select seq_test.nextval into :new.pk_no from dual;
   end if;
end;

谢谢！谢谢！
已经解决!