Re: Selecting newly added column returns empty but only when selecting with other columns in table - Mailing list pgsql-general

On 11/26/2015 06:10 PM, mrtruji wrote:

Hi,

Thanks for the reply. The limit is just to simplify results for the
examples. The same behavior occurs when each of the three queries are
not limited. Whenever I try to filter by the original columns and select
the new column the resultant values for the new column are empty.
Conversely, whenever I select the new column along with original columns
without any filtering the resultant values for the original columns
return empty. It's as if the added column is disconnected to the table
in some way causing problems with queries that combine original columns
and the new one.

I created and filled in the new column externally using psycopg2 in
Python so I'm not sure if that could be the source of the problem...

Just had a thought. Wondering if when you populated the table you added all the new_col values without actually populating the other fields. So now you have existing rows with the non new_col fields populated and another set of rows with new_col populated but not the other fields. Your table definition allows NULL in all fields so the above is possible.

What happens if you do:

Select * from data where new_col IS NOT NULL;

select * from data where new_col IS NULL;

On Thu, Nov 26, 2015 at 5:39 PM, Melvin Davidson <melvin6925@gmail.com
<mailto:melvin6925@gmail.com>> wrote:

    Is it possible you have more than one row where state = 'CA'?
    Putting a LIMIT 1 would then restrict to only 1 row.
    Have you tried with no limit? IE:|SELECT new_col FROM data;

    |

    On Thu, Nov 26, 2015 at 7:13 PM, mrtruji <mrtruji@gmail.com
    <mailto:mrtruji@gmail.com>> wrote:

        Just added a new bytea type column to an existing psql table and
        populated the column entirely with row data. Running into some
        strange query results:

        When I select the newly added column by itself I get all the
        data as expected:

        |SELECT new_col FROM data LIMIT 1; Result: \x8481e7dec3650040b.... |

        When I try to filter with 'where' on another column in the
        table, I get the values from the other columns as expected but
        empty from my new_column:

        |SELECT id, state, new_col FROM data WHERE state='CA' limit 1;
        Result: 123456_1; CA; EMPTY ROW |

        The reverse is also true. If I select my new column in
        combination with other columns with no 'where' I get the correct
        value from my new column but empty for the other columns:

        |SELECT id, state, new_col FROM data limit 1; Result: EMPTY ROW;
        EMPTY ROW; \x8481e7dec3650040b....|

        Thanks to anyone with advice!




    --
    *Melvin Davidson*
    I reserve the right to fantasize.  Whether or not you
    wish to share my fantasy is entirely up to you.

--
Adrian Klaver
adrian.klaver@aklaver.com