cppcms-users

[Cppcms-users] cppdb::statement.affected() usage?

[CN <cn...@gr...>]

Hello!

The following SELECT gets one tuple:

cppdb::statement st=session << "SELECT 1 FROM t1";
cppdb::result r=st.row();

Now, r.empty() returns false, which is correct, but st.affected() returns  
0.

cppdb::statement.affected() is supposed to return the selected number of  
tuples, which is 1 in this case, not 0.

Do I misunderstand its usage?

Thank you in advance!

Regards,
CN

Re: [Cppcms-users] cppdb::statement.affected() usage?

[Artyom <art...@ya...>]

> Hello!
> 
> The following SELECT gets one tuple:
> 
> cppdb::statement  st=session << "SELECT 1 FROM t1";
> cppdb::result r=st.row();
> 
> Now,  r.empty() returns false, which is correct, but st.affected() returns  
> 0.
> 
> cppdb::statement.affected() is supposed to return the selected  number of  
> tuples, which is 1 in this case, not 0.
> 
> Do I  misunderstand its usage?
> 


Yes, number of affected rows is number of rows affected by 
statements like DELETE or UPDATE, the behavior of  affected()
when using queries (like SELECT) is undefined and may cause 
exceptions.

Artyom




 
____________________________________________________________________________________
Need Mail bonding?
Go to the Yahoo! Mail Q&A for great tips from Yahoo! Answers users.
http://answers.yahoo.com/dir/?link=list&sid=396546091

Re: [Cppcms-users] cppdb::statement.affected() usage?

[CN <cn...@gr...>]

Thank you a lot for the clarification!

> Yes, number of affected rows is number of rows affected by
> statements like DELETE or UPDATE, the behavior of  affected()
> when using queries (like SELECT) is undefined and may cause
> exceptions.

It will save users much time if this behavior is documented.

Also, it will be handy if the number of selected rows (returned by libpq's  
PQntuples()) is implemented in either cppdb::statement or cppdb::result.  
Without this feature, it seems that iterating cppdb::result (by calling  
next()) is the only available way to know the number of selected rows.  
Wrong?

Regards,
CN

Re: [Cppcms-users] cppdb::statement.affected() usage?

[Artyom <art...@ya...>]

> Subject: Re: [Cppcms-users] cppdb::statement.affected() usage?
> 
> Thank you a lot for the clarification!
> 
> > Yes, number of affected rows  is number of rows affected by
> > statements like DELETE or UPDATE, the  behavior of  affected()
> > when using queries (like SELECT) is  undefined and may cause
> > exceptions.
> 
> It will save users much time  if this behavior is documented.
> 

It is documented the term "affected" is something known in general
for SQL handling.

> Also, it will be handy if the number of  selected rows (returned by libpq's  
> PQntuples()) is implemented in  either cppdb::statement or cppdb::result.  
> Without this feature, it  seems that iterating cppdb::result (by calling  
> next()) is the only  available way to know the number of selected rows.  
> Wrong?
> 

The problem is this is not always known as you get the data by iterating
over it so in some backends like sqlite3 you can know this only
after fully iterating the entire data set and somethimes it is not
so good idea.

So this option is not supported as in some cases the data is not fetched
in whole.

Artyom



      

[Cppcms-users] wiki documentation Re: cppdb::statement.affected() usage?

[augustin <aug...@ov...>]

On Wednesday 16 February 2011 12:11:17 am CN wrote:
> It will save users much time if this behavior is documented.


First, as Artyom pointed out, this is a SQL feature and it IS documented: 
check your SQL vendor documentation.

Second, you and everyone else on this list are welcome to contribute what you 
can to the CPPCMS wiki. Registration is easy. 
The number of contributors in the wiki (including occasional contributors like 
myself) sadly is far from matching the number of CPPCMS users.

CN: I am looking forward to your contributions in the wiki.

Blessings,

Augustin.


-- 
Friends: http://www.reuniting.info/ http://activistsolutions.org/
My projects:
http://astralcity.org/ http://3enjeux.overshoot.tv/ http://linux.overshoot.tv/ 
http://overshoot.tv/ http://charityware.info/ http://masquilier.org/
http://openteacher.info/ http://minguo.info/ 
http://www.wechange.org/ http://searching911.info/












.