Question

当我使用多个OR语句在一个sql语句中组合查询时，单个OR语句返回的记录数不会返回相同数量的记录。有人可以建议吗？

例如：

public class TemperatureConverterGUI extends javax.swing.JFrame {

/**
 * Creates new form TemperatureConverterGUI
 */
public TemperatureConverterGUI() {
    initComponents();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    button_convert = new javax.swing.JButton();
    edittext = new javax.swing.JFormattedTextField();
    label = new javax.swing.JLabel();
    label_resultat = new javax.swing.JLabel();
    resultat = new javax.swing.JLabel();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    button_convert.setText("Converteix");
    button_convert.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            button_convertActionPerformed(evt);
        }
    });

    edittext.setFormatterFactory(new javax.swing.text.DefaultFormatterFactory(new javax.swing.text.NumberFormatter(new java.text.DecimalFormat("#0"))));
    edittext.setHorizontalAlignment(javax.swing.JTextField.CENTER);
    edittext.setToolTipText("Introdueix un número en Fahrenheit");

    label.setText("Introdueix un número en Fahrenheit:");

    label_resultat.setText("Resultat: ");

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(49, Short.MAX_VALUE)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(label_resultat)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(resultat))
                .addComponent(button_convert)
                .addComponent(label)
                .addComponent(edittext, javax.swing.GroupLayout.PREFERRED_SIZE, 212, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(90, 90, 90))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(65, Short.MAX_VALUE)
            .addComponent(label)
            .addGap(12, 12, 12)
            .addComponent(edittext, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(31, 31, 31)
            .addComponent(button_convert)
            .addGap(48, 48, 48)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(label_resultat)
                .addComponent(resultat))
            .addGap(70, 70, 70))
    );

    pack();
}// </editor-fold>                        

private void button_convertActionPerformed(java.awt.event.ActionEvent evt) {                                               
    int f = Integer.valueOf(edittext.getText());
    int c = VisualTemperatureConverter.FahrenheitToCelsius(f);
    resultat.setText(String.valueOf(c));
}                                              

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(TemperatureConverterGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(TemperatureConverterGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(TemperatureConverterGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(TemperatureConverterGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    **TemperatureConverterGUI frame = new TemperatureConverterGUI();

    frame.button_convert.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER,0), "enter");
    frame.button_convert.getActionMap().put("enter", frame.button_convert.getAction());**


    frame.setVisible(true);
}

// Variables declaration - do not modify                     
private javax.swing.JButton button_convert;
private javax.swing.JFormattedTextField edittext;
private javax.swing.JLabel label;
private javax.swing.JLabel label_resultat;
private javax.swing.JLabel resultat;
// End of variables declaration
}

合并查询：

$sql1 = SELECT * FROM table_1 WHERE x = '0';
$sql2 = SELECT * FROM table_1 WHERE y = '0';
$sql3 = SELECT * FROM table_1 WHERE z = '0';

我从sql_total返回的记录数与通过将sql1，sql2和sql3组合返回的记录数相加而返回的合并记录数不同。我哪里错了？

Answer 1

您可能对此查询的结果感兴趣：

select (x = '0') as xzero, (y = '0') as yzero, (z = '0') as zzero, count(*),
       min(id), max(id)
from t
group by (x = '0'), (y = '0'), (z = '0');

这将显示您有许多行具有不同的条件组合是真的。我包含id以供进一步调查。

在SQL中使用多个OR条件

1 个答案: