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Question in JDBC

Posted on 1997-08-29
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Last Modified: 2010-04-16
I'm using JDBC to execute "select customer_name from customer where customer_num = ? " in database by calling prepareStatement->setInt(1,n)->executeQuery->getString.
But the result is correct for the first attempt only. When I using a for-loop to change variable n and all of the results will become the same as the first record I retrieved! Please give me some advice on how to use prepareStatement correctly! Thank you for your help!
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Question by:tomytsui
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5 Comments
 
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Accepted Solution

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sunot earned 100 total points
ID: 1226014
I don't really quite see your problem as the steps you took are correct. Maybe you could show a portion of your code.

But in your case, remember that you need 2 loops, one is for the changing value of n and the other for the various records retrieved for that particular n.

What I mean here is if each customer_num has several customer_name, then you'll need these loops.

For example, in a for loop, you could code something like this :

for (.........) {
   prepare.clearParameters();
   prepare.setInt(1,n);
   ResultSet results = prepare.executQuery();
   while (results.netx()) {
      ......... results.getString(1)....;
   }
}

I hope this helps you. A portion of your code could help in determining the cause to that mishap.
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Author Comment

by:tomytsui
ID: 1226015
Is that means I should clearParameter() before setInt again?
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Expert Comment

by:sunot
ID: 1226016
The clearParameter is just there to ensure that all the older parameter values are removed before specifying a new one. This is so that you wouldn't have a concat value of the parameter in use.
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Author Comment

by:tomytsui
ID: 1226017
Thank you very much
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Author Comment

by:tomytsui
ID: 1226018
I have tried your method in prepare query statement, it is not working as before! But I try to use prepareStatement to perform insert or update statements, they work well! So I think there is something wrong in ResultSet returned by executeQuery(), it always store the result of the first attempt!

Please comment on it again!
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