display problem when query is empty!?

[Jerome]

Hi,

I've got the following problem:

I want my ASP page to display a certain number (based on a COUNT query),
it works fine if the result is at least 1! If there are no records to be
counted (= the query is empty), I get errors.

What I've tried is this:

if rsNP_MB_Site.BOF = true or rsNB_MB_Site.EOF = true then
response.write "amount: 0"
else
response.write "amount: " & response.write
rsNP_MB_Site.Fields.Item("NP").Value
end if

But I keep getting an 'object required' error?

I've also tried with isnull(rsNP_MB_Site.Fields.Item("NP").Value) but
that didn't work out either.

Any help is greatly appreciated,

Jerome

 

[Evertjan.]

Jerome wrote on 31 aug 2004 in microsoft.public.inetserver.asp.general:

I've got the following problem:

I want my ASP page to display a certain number (based on a COUNT
query), it works fine if the result is at least 1! If there are no
records to be counted (= the query is empty), I get errors.

A reasonable ;-) correct SQL count() will return a valid 0 count

What I've tried is this:

if rsNP_MB_Site.BOF = true or rsNB_MB_Site.EOF = true then

if rsNP_MB_Site.BOF = true or rsNB_MB_Site.EOF = true then
is the same as just:
if rsNP_MB_Site.BOF or rsNB_MB_Site.EOF then

response.write "amount: 0"
else
response.write "amount: " & response.write
rsNP_MB_Site.Fields.Item("NP").Value

This is vbs nonsense, should be:

response.write "amount: " & rsNP_MB_Site.Fields.Item("NP").Value

but how can this "Item" be the result of a SQL count() ?

end if

I suggest you show your code and specify the db-engine and connection
type.

 

[Jerome]

Hi, sorry for my messed up coding ...

Here's the SQL code (accessing an Access DB):

SELECT Count(museebus_Site.IDUmeldung) AS NP
FROM museebus_Site GROUP BY museebus_Site.printed HAVING
(((museebus_Site.printed)=No));

What I want to do is display on a summary page how many records there
are which are still un-printed (hence the count).

But if there are no unprinted records, the query is empty instead of
having 0.

Thanks for any help.

Jerome

 

[Evertjan.]

Jerome wrote on 31 aug 2004 in microsoft.public.inetserver.asp.general:

Hi, sorry for my messed up coding ...

Here's the SQL code (accessing an Access DB):

SELECT Count(museebus_Site.IDUmeldung) AS NP
FROM museebus_Site GROUP BY museebus_Site.printed HAVING
(((museebus_Site.printed)=No));

What I want to do is display on a summary page how many records there
are which are still un-printed (hence the count).

Why not simply [something like/not tested]:

SQL="SELECT Count(*) AS NP FROM museebus_Site "_
"WHERE printed = 'No'"

And then [assuming the table has records]:

x.execute(SQL)

response.write "amount: " & x("NP")

 

[Jerome]

That works fine!

Thanks.

Jerome wrote on 31 aug 2004 in microsoft.public.inetserver.asp.general:

Hi, sorry for my messed up coding ...

Here's the SQL code (accessing an Access DB):

SELECT Count(museebus_Site.IDUmeldung) AS NP
FROM museebus_Site GROUP BY museebus_Site.printed HAVING
(((museebus_Site.printed)=No));

What I want to do is display on a summary page how many records there
are which are still un-printed (hence the count).

Why not simply [something like/not tested]:

SQL="SELECT Count(*) AS NP FROM museebus_Site "_
"WHERE printed = 'No'"

And then [assuming the table has records]:

x.execute(SQL)

response.write "amount: " & x("NP")

 

[Bob Barrows [MVP]]

Hi, sorry for my messed up coding ...

Here's the SQL code (accessing an Access DB):

SELECT Count(museebus_Site.IDUmeldung) AS NP
FROM museebus_Site GROUP BY museebus_Site.printed HAVING
(((museebus_Site.printed)=No));

Evertian has it correct. You are confused about when it is correct to use
Having instead of Where. The simple explanation is: WHERE conditions are
applied BEFORE the records are grouped and aggregations are calculated.
HAVING conditions are applied AFTER the grouping. Whenever possible, you
should use WHERE, because the fewer records you supply to the grouping
mechanism, the better your query will perform. Only use HAVING conditions
when you need to evaluate the records after the grouping and aggregation are
completed.


Some guidelines:
1. If the field you wish to filter appears in the GROUP BY clause, use WHERE

Select a, sum(b)
from table
where a = 3
group by a

This query will return a single row

2. If you wish to limit the resultset based on the result of an aggregation,
use HAVING

Select a, sum(b)
from table
group by a
HAVING sum(b) > 25

This query will return only rows where the sum is greater than 25.

3. If the field you are grouping by does not appear in the SELECT list, then
there is no need to put it in the GROUP BY clause:

Select sum(b)
from table
where a = 3

This query will again return a single row

4. If the field you wish to filter appears neither in the GROUP BY list nor
the SELECT list, use WHERE:

Select a, sum(b)
from table
where c = 3
group by a
HAVING sum(b) > 25


The reason that your query returned no records is because the HAVING clause
was applied to the records resulting from the grouping operation. These
records contained no field called printed, so the HAVING condition could
never be satisfied, resulting in no records being returned.

HTH,
Bob Barrows