如何在單個圖形上從兩個不同的MySQL表生成結果

Question

我想生成一個具有兩列的圖形。 一個將用於報價，另一個將用於發票（將比較兩個）。 該報價和發票是兩個所謂的分離表quotedb和invoicedb 。 我的問題是我只能讓它生成報價。 我是圖形新手，所以我的問題是，如何處理下面的編碼，以便它可以顯示兩個圖形中的數據。

這是從quotedb調用數據的quotedb ：

//declaring the type of category in the column
String text =cboQIMonth.getSelectedItem().toString();
String empno = cboEmployee.getSelectedItem().toString();
String year = cboQIYear.getSelectedItem().toString();

//connecting the database
Class.forName("com.mysql.jdbc.Driver");
Connection con = (Connection)
DriverManager.getConnection("jdbc:mysql://localhost:3306/salventri","root","password");
//select statement to retrieve data for the graph
PreparedStatement stmt = con.prepareStatement("select * from quotedb where EXTRACT(MONTH from quote_date)='" + monthnum + "' and EXTRACT(YEAR from quote_date) ='" + year + "' and username=" + empno +"");
ResultSet rs = stmt.executeQuery();
DefaultCategoryDataset ddataset = new DefaultCategoryDataset();
while (rs.next() ) 
{
    //data to be displayed on the graph 
    ddataset.setValue(rs.getInt("quote_total"),
    rs.getString("quote_number") + " by " + rs.getInt("username"),
    monthnum + " " + cboQIYear.getSelectedItem().toString());                            
}

Answer 1

如果可能，請在SQL查詢中合並兩個表，以便獲得包含所有所需數據的單個ResultSet。

如果quote_db包含以下內容：

+----------+-------------+
| QUOTE_ID | QUOTE_TOTAL |
+----------+-------------+
| quoteA   |          90 |
| quoteB   |         190 |
| quoteC   |         290 |
| quoteD   |         390 |
+----------+-------------+

並且invoice_db包含以下內容：

+------------+---------------+----------+
| INVOICE_ID | INVOICE_TOTAL | QUOTE_ID |
+------------+---------------+----------+
| invoiceA   |           100 | quoteA   |
| invoiceB   |           200 | quoteB   |
| invoiceC   |           300 | quoteC   |
| invoiceD   |           400 | quoteD   |
+------------+---------------+----------+

然后這段代碼：

PreparedStatement stmt = con.prepareStatement("select * from INVOICE_DB as iv, QUOTE_DB as qt where qt.QUOTE_ID = iv.QUOTE_ID");
ResultSet rs = stmt.executeQuery();
DefaultCategoryDataset ddataset = new DefaultCategoryDataset();
while (rs.next()) {
    ddataset.setValue(rs.getInt("invoice_total"),
           "invoice_total",
           rs.getString("invoice_id"));
    ddataset.setValue(rs.getInt("quote_total"),
           "quote_total",
           rs.getString("invoice_id"));
}
JFreeChart chart = ChartFactory.createBarChart3D("Compare Invoice and Quote", "Invoice ID's", "total", ddataset);
chart.getTitle().setPaint(Color.RED);
CategoryPlot p = chart.getCategoryPlot();
p.setRangeGridlinePaint(Color.BLUE);
ChartFrame frame2 = new ChartFrame("Compare Invoice and Quote", chart);
frame2.setVisible(true);
frame2.setSize(450, 350);

會產生這種情節：

如果不合理地加入他們，可以只做兩個查詢：

PreparedStatement stmt = con.prepareStatement("select * from INVOICE_DB");
ResultSet rs = stmt.executeQuery();
DefaultCategoryDataset ddataset = new DefaultCategoryDataset();
while (rs.next()) {
    ddataset.setValue(rs.getInt("invoice_total"),
           "invoice_total",
           rs.getString("invoice_id"));
}
stmt = con.prepareStatement("select * from QUOTE_DB");
rs = stmt.executeQuery();
while (rs.next()) {
    ddataset.setValue(rs.getInt("quote_total"),
           "quote_total",
           rs.getString("quote_id"));
}
JFreeChart chart = ChartFactory.createBarChart3D("Compare Invoice and Quote", "Invoice ID's", "total", ddataset);
chart.getTitle().setPaint(Color.RED);
CategoryPlot p = chart.getCategoryPlot();
p.setRangeGridlinePaint(Color.BLUE);
ChartFrame frame2 = new ChartFrame("Compare Invoice and Quote", chart);
frame2.setVisible(true);
frame2.setSize(450, 350);

生成的圖不容易比較發票和報價：