Thread: problems with SELECT query results

Hello,

I am new to this list and have been working with PostgreSQL since January.

Here is my problem, I hope someone here has some experience or can point 
me in the right direction. I am writing the following query for a C# 
program I am writing:

SELECT 'PV.LINEITEM:' || partnum || ',' || round(onhand) || ',' || 
round(qm5) || ',' || round(lsm4) || ',' || ',' || ',' || round(onorder) 
|| ',' || ',' || ',' || binone || ',' || ',' || round(backorderqty) || 
',' || ',' || round(onhold) || ',' || ',' || ',' || ',' || ',' || ',' || 
',' || round(qtyperjob) || ',' || round(ordermax) AS gmrim FROM slparts 
WHERE vendor LIKE 'CH%'

The query does work and I am getting results from the database. There 
are values for all 'partnum' in the database, however, the query results 
include blank fields here and there in between the returned records. Why 
am I receiving blank fields for 'gmrim'???? This absolutely defies logic 
and I cannot find any rhyme or reason for this problem. I cannot have 
any blank rows in the query, and again the database is completely 
populated with values.

Could someone give me an explanation or tell me why I am receiving blank 
rows here and there as a query result. If you need further clarification 
of this problem or have any questions for me to arrive at a conclusion 
please feel free to send them to me and I will be more than happy to 
open a dialog in order to solve this problem.

Thanks in advance for assistance.

Cordially,
Joshua Neil

Joshua wrote:
> Hello,
> 
> I am new to this list and have been working with PostgreSQL since January.
> 
> Here is my problem, I hope someone here has some experience or can point 
> me in the right direction. I am writing the following query for a C# 
> program I am writing:
> 
> SELECT 'PV.LINEITEM:' || partnum || ',' || round(onhand) || ',' || 
> round(qm5) || ',' || round(lsm4) || ',' || ',' || ',' || round(onorder) 
> || ',' || ',' || ',' || binone || ',' || ',' || round(backorderqty) || 
> ',' || ',' || round(onhold) || ',' || ',' || ',' || ',' || ',' || ',' || 
> ',' || round(qtyperjob) || ',' || round(ordermax) AS gmrim FROM slparts 
> WHERE vendor LIKE 'CH%'
> 
> The query does work and I am getting results from the database. There 
> are values for all 'partnum' in the database, however, the query results 
> include blank fields here and there in between the returned records. Why 
> am I receiving blank fields for 'gmrim'???? This absolutely defies logic 
> and I cannot find any rhyme or reason for this problem. I cannot have 
> any blank rows in the query, and again the database is completely 
> populated with values.

I'm not sure it is - I think you've got a NULL somewhere.

Since NULL means "unknown" ('text' || NULL) = NULL

Wrap all your column-references in COALESCE: e.g. COALESCE(partnum,'') 
and see if that solves it. If so, go back and find rows WHERE partnum IS 
NULL and correct them. Then set the NOT NULL constraint on the relevant 
columns.

--   Richard Huxton  Archonet Ltd

Hello,

Thank you all for your assistance. I did end up finding NULL in the 
'onorder' column which should have been zero's.... this was in a test 
table that happened to have some NULL in it for one reason or another 
but I should not find this in the production version of the table.

I also appreciate you pointing out the COALESCE function. I will find 
that helpful in future work.

I look forward to hopefully assisting you guys with some of your 
PostgreSQL dilemmas in the future!

Thanks again!!!

-Joshua

Richard Huxton wrote:
> Joshua wrote:
>> Hello,
>>
>> I am new to this list and have been working with PostgreSQL since 
>> January.
>>
>> Here is my problem, I hope someone here has some experience or can 
>> point me in the right direction. I am writing the following query for 
>> a C# program I am writing:
>>
>> SELECT 'PV.LINEITEM:' || partnum || ',' || round(onhand) || ',' || 
>> round(qm5) || ',' || round(lsm4) || ',' || ',' || ',' || 
>> round(onorder) || ',' || ',' || ',' || binone || ',' || ',' || 
>> round(backorderqty) || ',' || ',' || round(onhold) || ',' || ',' || 
>> ',' || ',' || ',' || ',' || ',' || round(qtyperjob) || ',' || 
>> round(ordermax) AS gmrim FROM slparts WHERE vendor LIKE 'CH%'
>>
>> The query does work and I am getting results from the database. There 
>> are values for all 'partnum' in the database, however, the query 
>> results include blank fields here and there in between the returned 
>> records. Why am I receiving blank fields for 'gmrim'???? This 
>> absolutely defies logic and I cannot find any rhyme or reason for 
>> this problem. I cannot have any blank rows in the query, and again 
>> the database is completely populated with values.
>
> I'm not sure it is - I think you've got a NULL somewhere.
>
> Since NULL means "unknown" ('text' || NULL) = NULL
>
> Wrap all your column-references in COALESCE: e.g. COALESCE(partnum,'') 
> and see if that solves it. If so, go back and find rows WHERE partnum 
> IS NULL and correct them. Then set the NOT NULL constraint on the 
> relevant columns.
>

--- Joshua <joshua@joshuaneil.com> wrote:

> Hello,
> 
> Thank you all for your assistance. I did end up finding NULL in the 
> 'onorder' column which should have been zero's.... this was in a test 
> table that happened to have some NULL in it for one reason or another 
> but I should not find this in the production version of the table.

If this should be allowed to have nulls, you should add a not null constraint to your table to
prevent this sort of thing from happening.  If a field should have zero's instead of nulls, you
should also add a default value of zero for this column.

ALTER TABLE Slparts ALTER COLUMN onorder SET NOT NULL, ALTER COLUMN onorder SET DEFAULT 0;

Regards,
Richard Broersma Jr.