java - 如何从Java传递sql命令

Question

我正在尝试传递一个 SQL 命令，其中必须从数据库中删除一行。 我正在使用 setString(index, value) 并调用主类中的方法。但是当我将参数传递给主类中的方法时，数据库中没有任何反应。有没有一个表单可以传递“jobnumber=”的值？在 main 方法中，它会从数据库中删除该行吗？ Ps:jobnumber被声明为序列号，并且是数据库中的主键。

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DeleteUserDao {
    Connection conDB2 = Connect.connectDB();    
    public void deleteDb(String y) {
        String sqlDelete = ("DELETE FROM bookings WHERE jobnumber=?");      
        try {
            PreparedStatement deleter = conDB2.prepareStatement(sqlDelete);
            deleter.setString(1, y);            
            System.out.println("Item deleted from Bookings.");
        } catch (SQLException e) {
            System.out.println("Coud not delete item. " + e.getMessage());
            e.printStackTrace();
        }
    }
}

import ***.jdbc.DeleteUserDao;

public class DeleteTest {
    public static void main(String[] args) {
        DeleteUserDao del = new DeleteUserDao();        
        del.deleteDb("4");
    }
}

Answer 1

如果我理解你的问题，那么你就错过了 executeUpdate()对于声明，

PreparedStatement deleter = conDB2.prepareStatement(sqlDelete);
deleter.setString(1, y);
deleter.executeUpdate(); // <-- like so

来自链接的 Javadoc，

Executes the SQL statement in this PreparedStatement object, which must be an SQL Data Manipulation Language (DML) statement, such as INSERT, UPDATE or DELETE; or an SQL statement that returns nothing, such as a DDL statement.

编辑

如下面的评论所述，您可能应该使用 int 类型，并且需要关闭 PreparedStatement -

public void deleteDb(int y) {
  String sqlDelete = ("DELETE FROM bookings WHERE jobnumber=?");     
  PreparedStatement deleter = null; 
  try {
    deleter = conDB2.prepareStatement(sqlDelete);
    deleter.setInt(1, y);            
    System.out.println("Item deleted from Bookings.");
  } catch (SQLException e) {
    System.out.println("Coud not delete item. " + e.getMessage());
    e.printStackTrace();
  } finally {
    if (deleter != null) {
      try {
        deleter.close();
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
}

然后调用它，传递一个 int -

del.deleteDb(4);