JDBC中的PreparedStatement

Posted 2020-08-12 何甜甜在吗

PreparedStatement类从Statement中继承来。

可以将SQL语句传给数据库做编译处理，即在执行的SQL语句中包含一个或多个IN参数，可以设置IN参数值多次执行SQL语句，不必重新给出SQL语句，提高了执行SQL语句的效率

import com.mysql.jdbc.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Properties;

/**
 * Created by I am master on 2016/10/3.
 */
public class preparedstatement {
    public static void main(String[] args)throws Exception {
       Class.forName("com.mysql.jdbc.Driver");
       String url="jdbc:mysql://localhost:3306/job";
       Properties info=new Properties();
       info.put("user","root");
       info.put("password","root");
       Connection connection= (Connection)DriverManager.getConnection(url,info);

        //IN参数用？表示
        String sql="select * from jobs where min_lvl>=? and max_lvl<=?";
        PreparedStatement preparedStatement=connection.prepareStatement(sql);
        //在执行查询操作之前必须对每个IN参数进行设置
        //设置IN参数的语法格式：preparedStatement.setXXX(position,value) position为IN参数在SQL语句中的位置，valu为参数被设置的值
        preparedStatement.setInt(1,160);
        preparedStatement.setInt(2,300);
        ResultSet rs=preparedStatement.executeQuery();

        while (rs.next()){
            String job_id=rs.getString("job_id");
            String job_desc=rs.getString("job_desc");
            String min_lvl=rs.getString("min_lvl");
            String max_lvl=rs.getString("max_lvl");

            System.out.print(job_id);
            System.out.print(job_desc);
            System.out.print(min_lvl);
            System.out.println(max_lvl);
        }
    }

}