Re: Select into

On Mar 20, 2008, at 7:10 AM, Joe wrote:

> Gavin 'Beau' Baumanis wrote:
>>
>> The copy is inside the same table, so I don't understand why it
>> (the required query ) would require any joins.
>>
>> Ie. I want to copy the contents of a row (but for the id column -
>> of course) into a record in the same table.
>
> I think what you want is something like this:
>
> Given (col1 being the id or PK):
>
> col1 | col2 | col3
> ------+------+---------------
> 1 | 123 | first record
> 2 | 456 | second record
> 3 | 789 | third record
>
> then
>
> update t1 set col2 = t1copy.col2, col3 = t1copy.col3
> from t1 as t1copy
> where t1.col1 = 1 and t1copy.col1 = 3;
>
> will result in:
>
> col1 | col2 | col3
> ------+------+---------------
> 1 | 789 | third record
> 2 | 456 | second record
> 3 | 789 | third record
>
> So, it is a join ... of a table with a virtual copy of itself.

Note that in 8.2.x and above you can write that as:

update t1
set (col2, col3) = (t1copy.col2, t1copy.col3)
from t1 as t1copy
where t1.col =1 and t1copy.col1=3;

Erik Jones

DBA | Emma®
erik(at)myemma(dot)com
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