Re: while (temp.next()) wont iterate - Rhino - com.mysql.lists.java

3 messages in com.mysql.lists.javaRe: while (temp.next()) wont iterate

From	Sent On	Attachments
Darko Kalevski	10 Nov 2005 08:15
Rhino	10 Nov 2005 09:32
Darko Kalevski	10 Nov 2005 11:10

Subject:	Re: while (temp.next()) wont iterate
From:	Rhino (rhi...@sympatico.ca)
Date:	11/10/2005 09:32:20 AM
List:	com.mysql.lists.java

Your example is somewhat confusing in some respects so I may say something that wouldn't make sense if I knew your language....

The first problem is that the example doesn't identify the type for variable 'temp'; is it a ResultSet?

Is the 'vratiRezultat()' method doing an 'executeQuery()'? I'm not sure what the 'y' variable in your example is either; I'm guessing it's an instance of a utility class you've created to do SQL for you....

Assuming that 'temp' is a ResultSet, are you absolutely certain that 4 rows satisfy the query? From the behaviour you are getting, it seems much more likely that only 1 row satisfies the query so the while loop only iterates once. The ResultSet.next() method should always iterate once for each row of the result set, no matter how many rows there are. If you are only getting one iteration, it seems VERY likely that only one row is satisfying the query. Please try the EXACT SAME query against the EXACT SAME table outside of Java and verify that it is returning 4 rows. Is there any chance that Java is pointing to a different version of the table, perhaps in a different database or server, that has only 1 row that satisfies the query?

If you're absolutely positive that the query will return 4 rows what happens when you run the program? Are you getting an error or does it only iterate the while loop once without throwing any exception?

If your Insert was failing it should be throwing an exception, which your code would catch. (By the way, I think you should be catching SQLException, not Exception, in your while loop.).

Are you aware that executeUpdate() returns an int that says how many rows were inserted? If you change 'dodadiRedica()' to return that int, then you can either display that int to make sure it is 1 or you can verify that it is 1 in your debugger. That would help verify that the Insert is succeeding.

booo! :)

hey folks, here it is a snippet of a code i'm writing and i ran onto very strange problem...well at least to me...please have a look at the code

temp=null; queryNasokiID="SELECT naspred_id FROM nasoki_predmeti WHERE semestar=1 AND institut=1 AND nasoka='Primeneta'"; temp=y.vratiRezultat(queryNasokiID);

try{ while (temp.next()){ String queryZapisiNasoki=""; queryZapisiNasoki="INSERT INTO upisi_predmeti (sk_god, student, semestar, naspred) VALUES (2005, 6266, 1, "+temp.getInt(1)+")"; y.dodadiRedica(queryZapisiNasoki); } }catch(Exception q){ q.printStackTrace(); }

well the while structue wont iterate, it just runs once and thats it. For example, with the values in the code it has to iterate 4 times, cause temp gives 4 rows with single column. which means i want to INSERT for rows in a different table subsequently. Is it something i'm doing wrong or?? I've tested the queries in MySQL Query Browser and they all work well. But once in a bean file...the while condition wont iterate...? And In the MySQL query browser I can do the INSERT query zillion times if I want to as long as I have different value for 'naspred' column. Like this: INSERT INTO upisi_predmeti (sk_god, student, semestar, naspred) VALUES (2005, 6266, 1, 1) INSERT INTO upisi_predmeti (sk_god, student, semestar, naspred) VALUES (2005, 6266, 1, 5) INSERT INTO upisi_predmeti (sk_god, student, semestar, naspred) VALUES (2005, 6266, 1, 9)

I can do them even within the bean place line after line, but once I try to generate generic INSERT statement and place it within the while condition...well it FAILS!

i've tried god knows how many combinations, initializing and etc...but it wont work...

here is dodadiRedici method which is a method part of another class and y is an object of that class:

public void dodadiRedica(String sql){ try{ statement.executeUpdate(sql); } catch (SQLException e) { System.err.println(sql); } }

thanks for looking!

darko