用表A中的字段b除以字段c，以字段d和f作为唯一标识，再用100减去b除以c的值

下面是一条可以用于 MySQL 的 SQL 查询语句，用于获取每个 ACTIVITY_NAME 字段值、ACTUAL_COST、ACTUAL_RETURN 以及 (ACTUAL_RETURN - ACTUAL_COST) / ACTUAL_COST 的结果： ```sql SELECT ACTIVITY_NAME, ACTUAL_COST, ACTUAL_RETURN, (ACTUAL_RETURN - ACTUAL_COST) / ACTUAL_COST AS RETURN_ON_COST FROM jmeta_campaigns; ``` 请确保将 `jmeta_campaigns` 替换为你实际的数据表名字。这条语句将返回一个结果集，其中包含每个 ACTIVITY_NAME 字段值、对应的 ACTUAL_COST、ACTUAL_RETURN，以及 (ACTUAL_RETURN - ACTUAL_COST) / ACTUAL_COST 的计算结果作为 RETURN_ON_COST 列。

以下是用Java实现布局计算器的代码： ```java import javax.swing.*; import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; public class Calculator extends JFrame implements ActionListener { private JLabel resultLabel; private JTextField inputField; private JButton clearButton; private JButton addButton; private JButton minusButton; private JButton multiplyButton; private JButton divideButton; private int accumulator; public Calculator() { setTitle("Calculator"); setSize(300, 200); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setLayout(new BorderLayout()); // 创建顶部的显示标签 resultLabel = new JLabel("0", JLabel.RIGHT); resultLabel.setFont(new Font("Arial", Font.PLAIN, 20)); add(resultLabel, BorderLayout.NORTH); // 创建中间的文本字段 inputField = new JTextField(); inputField.setFont(new Font("Arial", Font.PLAIN, 20)); add(inputField, BorderLayout.CENTER); // 创建底部的按钮 JPanel buttonPanel = new JPanel(new GridLayout(1, 5, 5, 5)); clearButton = new JButton("CLR"); addButton = new JButton("+"); minusButton = new JButton("-"); multiplyButton = new JButton("*"); divideButton = new JButton("/"); clearButton.addActionListener(this); addButton.addActionListener(this); minusButton.addActionListener(this); multiplyButton.addActionListener(this); divideButton.addActionListener(this); buttonPanel.add(clearButton); buttonPanel.add(addButton); buttonPanel.add(minusButton); buttonPanel.add(multiplyButton); buttonPanel.add(divideButton); add(buttonPanel, BorderLayout.SOUTH); setVisible(true); } public void actionPerformed(ActionEvent e) { if (e.getSource() == clearButton) { accumulator = 0; resultLabel.setText("0"); inputField.setText(""); } else { int value; try { value = Integer.parseInt(inputField.getText()); } catch (NumberFormatException ex) { value = 0; } if (e.getSource() == addButton) { accumulator += value; } else if (e.getSource() == minusButton) { accumulator -= value; } else if (e.getSource() == multiplyButton) { accumulator *= value; } else if (e.getSource() == divideButton) { if (value == 0) { JOptionPane.showMessageDialog(this, "除数不能为0！", "错误", JOptionPane.ERROR_MESSAGE); return; } accumulator /= value; } resultLabel.setText(String.valueOf(accumulator)); inputField.setText(""); } } public static void main(String[] args) { new Calculator(); } } ``` 运行该程序后，即可看到一个简单的布局计算器界面。用户可以在中间的文本字段中输入整数或者二进制数，然后点击底部的“+”、“-”、“*”、“/”按钮进行计算。点击“CLR”按钮可以清空输入和计算结果。