Changing a Field to Auto-Generation Type after Table is already created

Hello,
How do i change a Field to Auto Number type in Oracle SQL Developer after i have already created the Table?
i want to use this to map a File in Hibernate. or do i have to write some Hibernate code?
Any help would be greatly appreciated.
Thank you in advance

Hello,

try adding the follwoing property in your hibernate mapping xml.

<generator class="increment">
</generator>

I think this would help you.

i did that but when im trying to put "native" as the generator class, its starting from any number like 21 or 41. i though tit must start from 1. is it not like that?

Anupama Sudhakaran wrote:i did that but when im trying to put "native" as the generator class, its starting from any number like 21 or 41. i though tit must start from 1. is it not like that?

Why must it start from one? Does your primary key also have business meaning?

no it doesnt. i am writing small programs a si have just started learning Hibernate. in Access, when we select auto number for a field, it usually begins with 1 and keeps incrementing. does it not happenlike that in Oracle?

No. Sequences are usually used in Oracle to back primary key generation, so all you really need to know from these is:

the number is unique

the numbers are in order

You get the same semantic meaning from 1,2,3,4 as you get from 1,45,877,678768. However there is a performance cost in keeping sequence numbers consecutive. Without any benefit, why do it?

Thank you Paul