I don't this this is possible as postgres.
There is something simular with:
alter table table_name alter column column_foo using column_bar
But I don't think there's any performance advantage over a simple
update and the using clause doesn't appear to have an equivalent in an
add column statement.
You could.
alter table table_name rename column_foo to column_bar;
alter table table_name add column_foo foo_data_type default =
nextval('new_foo_sequence');
This has your best chance of success since renaming a column should
not have to touch every row of the table.
Regards
On 4 October 2011 20:21, J.V. <jvsrvcs@xxxxxxxxx> wrote:
> What I need to do is to save the id column for future use and then modify
> the id column resetting all values from another sequence.
>
> So I need to select the id column or somehow get the data into another
> column in the same table.
>
> And then I can update the id column (after dropping the constraint).
>
> J.V.
>
> On 10/4/2011 1:09 PM, Scott Marlowe wrote:
>>
>> On Tue, Oct 4, 2011 at 12:24 PM, J.V.<jvsrvcs@xxxxxxxxx> wrote:
>>>
>>> Currently I can select one column into another with two statements:
>>>
>>> alter table<table_name> add column id_old int;
>>> update<table_name> set id_old = id;
>>>
>>> Is there a way to do this in one statement with a select into? I have
>>> tried
>>> various select statements but want the new column (with the same data) to
>>> be
>>> in the same table and to have it execute much more quickly that the two
>>> statements currently do.
>>
>> Do you need another column or do you just want to alter a column that
>> already exists? If so you can alter a column from one type to another
>> and throw a using clause at it to convert the data in some way. I
>> think we need to know a bit better what you're trying to do.,
>>
>
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