JDBC中的CONCUR_UPDATABLE ResultSet是什么?说明?

它是ResultSet类的常量,表示可更新的ResultSet对象的并发模式。通常,您会将其作为值传递给createStatement() 方法。

Statement createStatement(int resultSetType, int resultSetConcurrency);

以此为并发的ResultSet是可更新的。即,一旦获得ResultSet对象,就可以更新其内容。

示例

假设我们在数据库中有一个名为Employee的表,其内容如下:

+----+---------+--------+----------------+

| Id | Name    | Salary | Location       |

+----+---------+--------+----------------+

| 1  | Amit    | 3000   | Hyderabad      |

| 2  | Kalyan  | 4000   | Vishakhapatnam |

| 3  | Renuka  | 6000   | Delhi          |

| 4  | Archana | 96000  | Mumbai         |

| 5  | Sumith  | 11000  | Hyderabad      |

| 6  | Rama    | 11000  | Goa            |

| 7  | Mahesh  | 5300   | Vishakhapatnam |

| 8  | Ramesh  | 12000  | Hyderabad      |

| 9  | Suresh  | 7600   | Pune           |

| 10 | Santosh | 96000  | Mumbai         |

+----+---------+--------+----------------+

下面的示例将员工的薪水值增加5000,并打印结果。由于我们在其中创建的ResultSet是可更新的,因此您可以对其进行更新并显示值。

import java.sql.*;

public class Updatable {

   public static void main(String [] args) throws Exception {

      //注册驱动程序

      DriverManager.registerDriver(new com.mysql.jdbc.Driver());

      //获得连接

      String mysqlUrl = "jdbc:mysql://localhost/TestDB";

      Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");

      System.out.println("Connection established......");

      //创建一个Statement对象

      Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,

      ResultSet.CONCUR_UPDATABLE);

      //检索数据

      ResultSet rs = stmt.executeQuery("select * from Employees");

      //打印表的内容

      System.out.println("Contents of the table: ");

      rs.beforeFirst();

      while(rs.next()) {

         System.out.print("ID: " + rs.getInt("id"));

         System.out.print(", Salary: " + rs.getInt("Salary"));

         System.out.print(", Name: " + rs.getString("Name"));

         System.out.println(", Location: " + rs.getString("Location"));

      }

      System.out.println();

      //的起点

      rs.beforeFirst();

      //每位员工的薪水提高5000-

      while(rs.next()) {

         //通过列名检索

         int newSal = rs.getInt("Salary") + 5000;

         rs.updateInt( "Salary", newSal );

         rs.updateRow();

      }

      System.out.println("Contents of the ResultSet after increasing salaries");

      rs.beforeFirst();

      while(rs.next()) {

         System.out.print("ID: " + rs.getInt("id"));

         System.out.print(", Salary: " + rs.getInt("Salary"));

         System.out.print(", Name: " + rs.getString("Name"));

         System.out.println(", Location: " + rs.getString("Location"));

      }

      System.out.println();

   }

}

输出结果

Connection established......

Contents of the table:

ID: 1, Salary: 3000, Name: Amit, Location: Hyderabad

ID: 2, Salary: 4000, Name: Kalyan, Location: Vishakhapatnam

ID: 3, Salary: 6000, Name: Renuka, Location: Delhi

ID: 4, Salary: 96000, Name: Archana, Location: Mumbai

ID: 5, Salary: 11000, Name: Sumith, Location: Hyderabad

ID: 6, Salary: 11000, Name: Rama, Location: Goa

ID: 7, Salary: 5300, Name: Mahesh, Location: Vishakhapatnam

ID: 8, Salary: 12000, Name: Ramesh, Location: Hyderabad

ID: 9, Salary: 7600, Name: Suresh, Location: Pune

ID: 10, Salary: 96000, Name: Santosh, Location: Mumbai

Contents of the ResultSet after increasing salaries

ID: 1, Salary: 8000, Name: Amit, Location: Hyderabad

ID: 2, Salary: 9000, Name: Kalyan, Location: Vishakhapatnam

ID: 3, Salary: 11000, Name: Renuka, Location: Delhi

ID: 4, Salary: 101000, Name: Archana, Location: Mumbai

ID: 5, Salary: 16000, Name: Sumith, Location: Hyderabad

ID: 6, Salary: 16000, Name: Rama, Location: Goa

ID: 7, Salary: 10300, Name: Mahesh, Location: Vishakhapatnam

ID: 8, Salary: 17000, Name: Ramesh, Location: Hyderabad

ID: 9, Salary: 12600, Name: Suresh, Location: Pune

ID: 10, Salary: 101000, Name: Santosh, Location: Mumbai

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