将以下代码添加到 executeQuery()
方法中:
public static void executeQuery() {
// 在此处编写代码
Connection connection = null;
Statement stmt = null;
ResultSet rs = null;
try{
// 在此处编写代码
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/edusys";
String username = "root";
String password = "";
connection = DriverManager.getConnection(url, username, password);
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the table to query:");
System.out.println("1. student");
System.out.println("2. course");
System.out.println("3. instructor");
int option = scanner.nextInt();
String sql = "";
switch (option) {
case 1:
sql = "SELECT ID, name, dept_name FROM student";
break;
case 2:
sql = "SELECT course_id, title, dept_name FROM course";
break;
case 3:
sql = "SELECT ID, name, dept_name FROM instructor";
break;
default:
System.out.println("Invalid option");
}
stmt = connection.createStatement();
rs = stmt.executeQuery(sql);
while (rs.next()) {
String column1 = rs.getString(1);
String column2 = rs.getString(2);
String column3 = rs.getString(3);
System.out.println(column1 + "\t" + column2 + "\t" + column3);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally{
try {
if(rs!= null)rs.close();
if(stmt!= null)stmt.close();
if(connection!= null)connection.close();
} catch (SQLException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
}
这段代码连接到 MySQL 数据库,提示用户选择要查询的表,执行相应的 SQL 查询,并将结果打印到控制台。