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Thread: Something wrong in my database SQL Logic(JDBC) , please correct me.

  1. #1
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    Default Something wrong in my database SQL Logic(JDBC) , please correct me.

    while (i < 7){
     
    		try{           
    		                Connection[] MainConnection = new Connection[7];
     
    						String[] RemoteIPAddress = new String[7];
     
    						RemoteIPAddress[0] = "aa.aa.a.aaa";
    						RemoteIPAddress[1] = "bb.bb.b.bbb";
    						RemoteIPAddress[2] = "cc.cc.c.ccc";
    						RemoteIPAddress[3] = "dd.dd.d.ddd";
    						RemoteIPAddress[4] = "ee.ee.e.eee";
    						RemoteIPAddress[5] = "ff.ff.f.fff";
    						RemoteIPAddress[6] = "gg.gg.g.ggg";
     
     
     
    						MainConnection[i] = DriverManager.getConnection("jdbc:mysql://" + RemoteIPAddress[i] + ":3306/test",RemoteUser,RemotePass);
     
     
    						Connection connRemote = DriverManager.getConnection("jdbc:mysql://xx.xx.x.xxx:3306/test",MainUser,MainPass);
     
     
    						}
     
    						catch(SQLException e){
     
    						}
     
    			}// END OF WHILE
    I am naming database located at xx.xx.x.xxx as Maindb for our discussion purpose. I have a table in the Maindb and column with name "IPStatus".
    So, basically for each IP addresses (starting from aa.aa.a.aaa to gg.gg.g.ggg), I have a value 0 or 1 set in the IPStatus column in the database.
    I want to basically establish connection to the above 7 databases only if the value of the IP Status is 1. So for example, if the value of IPStatus field is 1 for the IP addresses , namely, aa.aa.a.aaa,
    bb.bb.b.bbb and dd.dd.d.ddd and for others it's zero, so I would like to establish connection to only first three. I am doing Something like the following inside the aforementioned try-block:


    			while(i<7){
                      try{			
     
    							Connection[] MainConnection = new Connection[7];
     
    						    Connection[] MainConnection = new Connection[7];
     
     
    							RemoteIPAddress[0] = "aa.aa.a.aaa";
    							RemoteIPAddress[1] = "bb.bb.b.bbb";
    							RemoteIPAddress[2] = "cc.cc.c.ccc";
    							RemoteIPAddress[3] = "dd.dd.d.ddd";
    							RemoteIPAddress[4] = "ee.ee.e.eee";
    							RemoteIPAddress[5] = "ff.ff.f.fff";
    							RemoteIPAddress[6] = "gg.gg.g.ggg";
     
    							Connection connRemote = DriverManager.getConnection("jdbc:mysql://xx.xx.x.xxx:3306/test",MainUser,MainPass);
     
    							String maindbsql = "SELECT IPStatus 
    							FROM   Maindb.TableIPStatus ";
     
                                                            Statement stmt = connRemote.createStatement();
     
    							Resultset rs = stmt.executeQuery(maindbsql);
     
    						        while(rs.next()){	
     
    							int ipStatus = rs.getInt("IPStatus");                   
     
    							System.out.println("The value of ipStatus is:"+ipStatus);
     
    								if(ipStatus == 1)
    								{
    								MainConnection[i] = DriverManager.getConnection("jdbc:mysql://" + RemoteIPAddress[i] + ":3306/test",RemoteUser,RemotePass);
    								}
     
    						      }// END Of WHILE (rs.next())
     
     
    						}catch(SQLException e){
     
    						e.printStackTrace();
    						}
    					i++;
                } END OF ORIGINAL WHILE LOOP while (i < 7)


    But nothing happens after adding the additional code, not even the statement is getting printed `System.out.println("The value of ipStatus is:"+ipStatus);`

    Please suggest where I am wrong. Thanks

    --- Update ---

    My schema is defined here: SQL Fiddle
    Last edited by Jack_Tauson_Sr; March 27th, 2014 at 06:41 PM.


  2. #2
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    Default Re: Something wrong in my database SQL Logic(JDBC) , please correct me.

    catch(SQLException e){
     
     
    }

    Never ignore exceptions, which is what the above does. At the very least call printStackTrace() on the exception object so you can see the stack trace (with important information) on the command line. Post the stack trace here if it makes no sense.

  3. #3
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    Default Re: Something wrong in my database SQL Logic(JDBC) , please correct me.

    Thanks for your answer, I have printStackTrace() in my real code (updated the same here as well) but still wondering about the logic that I am using there. There are no exceptions thrown by my code.
    Last edited by Jack_Tauson_Sr; March 27th, 2014 at 06:45 PM.

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