Обсуждение: Need help to implement Primary Key.

Gambhir Singh schrieb am 08.02.2024 um 11:30:

> I have a table with a record count of ~500 million (496,098,390).
> There is no primary key in this table. Now I need to set up a primary
> key on this table. I can't find a way to set up a primary key. I
> tried to add a new column with IDENTITY but it is not allowing null
> value for existing rows and I don't know how to update the unique
> value for existing records.

If you add an identity column, it will automatically be populated


alter table foo
   add id bigint generated always as identity not null;

Once that has finished (which will take some time given the size of the table),
you can add the primary key:

alter table foo
   add constraint pk_foo primary key (id);

Am 08.02.24 um 11:37 schrieb Thomas Kellerer:
> Gambhir Singh schrieb am 08.02.2024 um 11:30:
>
>> I have a table with a record count of ~500 million (496,098,390).
>> There is no primary key in this table. Now I need to set up a primary
>> key on this table. I can't find a way to set up a primary key. I
>> tried to add a new column with IDENTITY but it is not allowing null
>> value for existing rows and I don't know how to update the unique
>> value for existing records.
> If you add an identity column, it will automatically be populated
>
>
> alter table foo
>     add id bigint generated always as identity not null;
>
> Once that has finished (which will take some time given the size of the table),
> you can add the primary key:
>
> alter table foo
>     add constraint pk_foo primary key (id);
>
You can even do this in one step:

alter table table1 add column id bigint primary key generated always as 
identity;

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