The result set has no current row

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I'm doing a program of Libros and Autores where a autor has many libros .

When inserting a new Libro I need to get id of autor to save it as fk_dni in table Libros , so I have the following code which loads me combobox with the Autores that are stored in my database. 

public void insertarLibro()
    {
        String url = "jdbc:sqlserver://localhost:1433;databaseName=Biblioteca";
        String user = "mi_usuario";
        String password = "mi_contraseña";
        String fk_dni = "SELECT dni FROM Autores WHERE nombre = '?'";


        try
        {
            Connection cn = DriverManager.getConnection(url, user, password);
            PreparedStatement ps = cn.prepareStatement(fk_dni);
            ResultSet rs = ps.executeQuery();
            String nombre = (String)cboAutor.getSelectedItem();

            while(rs.next())
            {
                ps.setString(1, nombre);
            }

            System.out.println("DNI : " + rs.getString(1));
        }
        catch(SQLException e)
        {
            System.out.println("ERROR : ");
            e.printStackTrace(System.out);
        }

    }

But my program returns the following error

  

com.microsoft.sqlserver.jdbc.SQLServerException: The set of   results has no current row

So I gather that my program is not entering my while loop. In case I delete the single quotes in my query fk_dni , the error that throws me is:

  

The value is not configured for parameter number 1.

The System.out.println("DNI : " + rs.getString(1)); is temporary since I only use it to confirm that the data is displayed correctly.

    
asked by Lucas. D 30.08.2017 в 20:12
source

2 answers

3

There are some errors in the code:

  • Written prepared query. The parameter or parameters that will be passed in the prepared statement, indicated by ? should not be surrounded by single quotes as you have it now. It should be: 

    String fk_dni = "SELECT dni FROM Autores WHERE nombre = ?";

  • You can not do executeQuery before setting the nombre parameter: 

    try
{
    String nombre = (String)cboAutor.getSelectedItem();
    Connection cn = DriverManager.getConnection(url, user, password);
    PreparedStatement ps = cn.prepareStatement(fk_dni);
    ps.setString(1, nombre);
    ResultSet rs = ps.executeQuery();

    if(rs.next())
    {
       System.out.println("DNI : " + rs.getString(1));
    }

}
catch(SQLException e)
{
    System.out.println("ERROR : ");
    e.printStackTrace(System.out);
}

Note: Searching for a DNI just by name may give you wrong information, maybe José Egypt's is not the same as José the one in Nazareth.

answered by 30.08.2017 / 20:23
source
4

As @ A.Cedano said, the query does not have single quotes in the question mark: 

String fk_dni = "SELECT dni FROM Autores WHERE nombre = ?";

Also, you have to pass the value to the query and then execute it 

 public void insertarLibro()
    {
    String url = "jdbc:sqlserver://localhost:1433;databaseName=Biblioteca";
    String user = "mi_usuario";
    String password = "mi_contraseña";
    String fk_dni = "SELECT dni FROM Autores WHERE nombre = ?";


    try
    {
        Connection cn = DriverManager.getConnection(url, user, password);
        PreparedStatement ps = cn.prepareStatement(fk_dni);
        String nombre = (String)cboAutor.getSelectedItem();
        ps.setString(1, nombre);
        ResultSet rs = ps.executeQuery();
        while(rs.next())
           System.out.println("DNI : " + rs.getString(1));
    }
    catch(SQLException e)
    {
        System.out.println("ERROR : ");
        e.printStackTrace(System.out);
    }

}
    
answered by 30.08.2017 в 20:25
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