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Thread: How to properly use a record which has a composite key in mySQL code in Java

  1. #1
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    Question How to properly use a record which has a composite key in mySQL code in Java

    So I am making a small software for a Hotel Management System and I need some help calling the values from the database. In my database I have a table called "keys". This table has the following columns: idfood , iditem , amount. 'idfood' and 'iditem' are both primary keys forming a composite key.

    This is what the database looks like with test values : database.JPG

    Now I made an interface in NetBeans which looks like this: interface.JPG

    What I want to happen is, when I enter a value in the text box (For example '1') all the records which have idfood as '1' should display in the table. I would appreciate any help.

    Following is my code (the button named 'Search'):

     
        DefaultTableModel dtm = (DefaultTableModel) jTable1.getModel();
     
        String a = jTextField1.getText();
     
        try {
     
            Statement s = DB.getConnection().createStatement();
            ResultSet rs = s.executeQuery("SELECT * FROM keys WHERE idfood = '"+a+"'");
     
            while(rs.next()){
     
                Vector v = new Vector();
                v.add(rs.getString("idfood"));
                v.add(rs.getString("iditem"));
                v.add(rs.getString("amount"));
     
                dtm.addRow(v);
            }
        } 
     
        catch (Exception e) {
            e.printStackTrace();
        }

    When I run the above code I get the following error in NetBeans 7.3:
    com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorEx ception: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'keys WHERE idfood = '1'' at line 1

    Please help. I'm still a bit new to java. Still a student. So please don't use complicated jargon. Much appreciated
    Last edited by AnkleBreaker; May 6th, 2014 at 11:30 AM. Reason: Adding tags


  2. #2
    Administrator copeg's Avatar
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    Default Re: How to properly use a record which has a composite key in mySQL code in Java

    Please wrap all code using the proper code tags to preserve formatting, and please read Announcements - What's Wrong With My Code?

    com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorEx ception: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'keys WHERE idfood = '1'' at line 1
    First, I'd recommend using a PreparedStatement - its cleaner and prevents injection. Second, you said your table name is KOT, but you are selecting from keys?

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    Default Re: How to properly use a record which has a composite key in mySQL code in Java

    Thanks for you reply

    First off, I didn't know about the tagging thing. I'm very sorry about that.

    2nd: I'm not sure how to use a PreparedStatement. In my college they just taught us the way I have shown above. I tried to watch a video tutorial on PreparedStatement but it was not very clear. Could you please edit my code using PreparedStatement?

    3rd: Yeah, I'm sorry about the confusion. In the final project, the table will be named KOT. I named the table "keys" as I wanted to first test out the composite key method. I'll edit my question accordingly.

    Again, thanks for you reply.

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    Default Re: How to properly use a record which has a composite key in mySQL code in Java

    See Using Prepared Statements (The Java™ Tutorials > JDBC(TM) Database Access > JDBC Basics)

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