Oracle 11g：使用自动增量long值将列添加到EXISTING表中

Question

I have a table, say Name, (I simplify the example for simplicity). This table already exists, and has data. Now, I need to add an ID column of type long to it, and need to make the value auto incremented.

For Oracle 12c, this is easy with generated always as identity .

However, I work on Oracle 11g, and such a feature is not supported. So I needed to create a trigger, as described in this post: How to create id with AUTO_INCREMENT on Oracle?

alter table name add (id integer);

create sequence name_seq;

create or replace trigger name_bir;   
before insert on name
for each row
begin
 select name_seq.NEXTVAL
 into :new.id
 from dual;
end;

However, that solution (creating a sequence, and then a trigger on Insert/Update) only works when a new row is inserted. It doesn't apply to the existing rows in the table.

I'd appreciate any suggestion. Basically, I need BOTH the existing and the newly-inserted rows to have the new ID values for my newly added column ID.

=============================

Solution (collected from the answer):

1. Use "update" statement as posted by "a_horse_with_no_name" to update the existing rows

2. Still need a trigger above for any new rows that will be inserted.

Answer 1

After you created the sequence, just update the existing rows:

alter table name add (id integer);

create sequence name_seq;

update name 
  set id = name_seq.nextval;
commit;

There is no need for PL/SQL or a slow and in-efficient row-by-row processing in a LOOP.

---

Unrelated, but: the assignment in the trigger can be simplified to:

:new.id := name_seq.NEXTVAL;

No need for a select .. from dual

Answer 2

在添加ID列并按照您提到的那样创建NAME_SEQ序列之后，而不是使用循环，一个更简单的选择是使用Update语句，如下所示：

update NAME set ID= NAME_SEQ.nextval ;

Answer 3

This should do the trick

BEGIN
alter table name add (id integer);
create sequence name_seq;

FOR REC IN (SELECT * FROM NAME) LOOP
UPDATE NAME SET ID = NAME_SEQ.NEXTVAL 
WHERE ROWID = REC.ROWID;
END LOOP;
END;