如何选择几个相同的数据在mysql和视图在jComboBox java

Question

我有一个表01在MyDatabase01

注意:在netbeans中，id=jTextField1, day=jComboBox1, month=jComboBox2, year=jComboBox3

+=================================+
|id   |day      |month    |year   |
+=================================+
|A1   |monday   |january  |2016   |
|A2   |monday   |january  |2017   |
|A3   |sunday   |february |2016   |
|A4   |sunday   |march    |2016   |
|A5   |monday   |july     |2016   |
+=================================+

和，如何选择1月和7月中的一个，其中一天是星期一?这样的

+=========+
|month    |
+=========+
|january  |
|july     |
+=========+

那么，如何选择年份2016 &2017年哪一天是星期一?这样的

+=======+
|year   |
+=======+
|2016   |
|2017   |
+=======+

之后，我想查看月和年进入jComboBox java netbeans，这是我的代码

月的源代码

try {
        connectDB();
        jComboBox2.removeAllItems();
        String sql = "SELECT * FROM table01 WHERE day='"+jComboBox1.getSelectedItem()+"' UNION SELECT * FROM table01 WHERE day='"+jComboBox1.getSelectedItem()+"'"; 
//not work.always show all data, not january and july.
        ResultSet res = stat.executeQuery(sql);
        while (res.next()) {
            String val = res.getString("month");
            jComboBox2.addItem(val);
        }
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, e);
    }

年份的源代码

try {
        connectDB();
        jComboBox3.removeAllItems();
        String sql = "SELECT * FROM table01 WHERE month='"+jComboBox2.getSelectedItem()+"' AND day='"+jComboBox1.getSelectedItem()+"'"; 
//not work. always show all data, not 2016 and 2017.
        ResultSet res = stat.executeQuery(sql);
        while (res.next()) {
            String val = res.getString("year");
            jComboBox3.addItem(val);
        }
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, e);
    }

谢谢你的帮助

Answer 1

尝试如下。它将返回您所期望的。

月的源代码

   String sql = "SELECT DISTINCT(month) FROM table01 WHERE day='"+jComboBox1.getSelectedItem()"';
            ResultSet res = stat.executeQuery(sql);
            while (res.next()) {
                String val = res.getString(0);
                jComboBox2.addItem(val);
            }

年份的源代码

 String sql = "SELECT DISTINCT(year) FROM table01 WHERE month='"+jComboBox2.getSelectedItem()+"' AND day='"+jComboBox1.getSelectedItem()+"'"; 
        ResultSet res = stat.executeQuery(sql);
        while (res.next()) {
            String val = res.getString("0");
            jComboBox3.addItem(val);
        }

Answer 2

您可以使用以下命令:

select distinct(yourtable.month) from yourtable where UPPER(yourtable.day) = UPPER('monday')