JDBC - 更新结果集示例

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以下是示例，它使用了结果集教程中描述的ResultSet.CONCUR_UPDATABLE和ResultSet.TYPE_SCROLL_INSENSITIVE。本示例将解释在表上执行INSERT、UPDATE和DELETE操作。

需要注意的是，您正在使用的表应正确设置主键。

删除表并按如下方式重新创建表Employees：

mysql> use TUTORIALSPOINT;
mysql> drop table Employees;
Query OK, 0 rows affected (0.08 sec)
mysql> create table Employees
    -> (
    -> id int primary key auto_increment,
    -> age int not null,
    -> first varchar (255),
    -> last varchar (255)
    -> );
Query OK, 0 rows affected (0.08 sec)
mysql>

创建数据记录

最后，您按如下方式在Employee表中创建一些记录：

mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (18, 'Zara', 'Ali');
Query OK, 1 row affected (0.05 sec)

mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (25, 'Mahnaz', 'Fatma');
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (30, 'Zaid', 'Khan');
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO Employees(AGE, FIRST, LAST) VALUES (28, 'Sumit', 'Mittal');
Query OK, 1 row affected (0.00 sec)

mysql>

使用ResultSet示例更新和插入记录

在此示例中，我们有四个静态字符串，包含数据库连接URL、用户名、密码和SELECT查询。现在，使用DriverManager.getConnection()方法，我们准备了一个数据库连接。连接准备就绪后，我们使用connection.createStatement()方法创建了一个Statement对象。在创建Statement对象时，我们使用了ResultSet类型TYPE_SCROLL_INSENSITIVE和CONCUR_UPDATABLE，然后使用statement.executeQuery()执行SELECT查询，并将结果存储在结果集中。

我们定义了一个printResultSet()方法，用于打印所有记录。在主方法中，我们使用updateDouble()方法更新所有记录的年龄，并使用updateRow()更新记录。类似地，我们使用moveToInsertRow()标记结果集以插入记录。然后，使用updateString()和updateInt()方法添加新值，然后使用insertRow()方法提交更改，从而将记录插入数据库。现在，使用printResultSet()再次打印所有记录。

将以下示例复制并粘贴到ResultSetExample.java中，编译并运行如下：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class ResultSetExample {
   static final String DB_URL = "jdbc:mysql:///TUTORIALSPOINT";
   static final String USER = "guest";
   static final String PASS = "guest123";
   static final String QUERY = "SELECT id, first, last, age FROM Employees";

   public static void printResultSet(ResultSet rs) throws SQLException{
      // Ensure we start with first row
      rs.beforeFirst();
      while(rs.next()){
         // Display values
         System.out.print("ID: " + rs.getInt("id"));
         System.out.print(", Age: " + rs.getInt("age"));
         System.out.print(", First: " + rs.getString("first"));
         System.out.println(", Last: " + rs.getString("last"));
      }
      System.out.println();
   }

   public static void main(String[] args) {
      // Open a connection
      try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
         Statement stmt = conn.createStatement(
         ResultSet.TYPE_SCROLL_INSENSITIVE,
         ResultSet.CONCUR_UPDATABLE);
         ResultSet rs = stmt.executeQuery(QUERY);
      ) {		

         System.out.println("List result set for reference....");
         printResultSet(rs);

         // Loop through result set and add 5 in age
         // Move to Before first position so while-loop works properly
         rs.beforeFirst();
         //STEP 7: Extract data from result set
         while(rs.next()){
            // Retrieve by column name
            int newAge = rs.getInt("age") + 5;
            rs.updateDouble( "age", newAge );
            rs.updateRow();
         }
         System.out.println("List result set showing new ages...");
         printResultSet(rs);

         // Insert a record into the table.
         // Move to insert row and add column data with updateXXX()
         System.out.println("Inserting a new record...");
         rs.moveToInsertRow();
         rs.updateString("first","John");
         rs.updateString("last","Paul");
         rs.updateInt("age",40);
         // Commit row
         rs.insertRow();

         System.out.println("List result set showing new set...");
         printResultSet(rs);	

      } catch (SQLException e) {
         e.printStackTrace();
      } 
   }
}

输出

现在，我们按如下方式编译上述示例：

C:\>javac ResultSetExample.java
C:\>

运行ResultSetExample时，它会产生以下结果：

C:\>java ResultSetExample
List result set for reference....
ID: 1, Age: 18, First: Zara, Last: Ali
ID: 2, Age: 25, First: Mahnaz, Last: Fatma
ID: 3, Age: 30, First: Zaid, Last: Khan
ID: 4, Age: 28, First: Sumit, Last: Mittal

List result set showing new ages...
ID: 1, Age: 23, First: Zara, Last: Ali
ID: 2, Age: 30, First: Mahnaz, Last: Fatma
ID: 3, Age: 35, First: Zaid, Last: Khan
ID: 4, Age: 33, First: Sumit, Last: Mittal

Inserting a new record...
List result set showing new set...
ID: 1, Age: 23, First: Zara, Last: Ali
ID: 2, Age: 30, First: Mahnaz, Last: Fatma
ID: 3, Age: 35, First: Zaid, Last: Khan
ID: 4, Age: 33, First: Sumit, Last: Mittal
ID: 5, Age: 40, First: John, Last: Paul
C:\>

使用ResultSet示例插入和删除记录

在此示例中，我们有四个静态字符串，包含数据库连接URL、用户名、密码和SELECT查询。现在，使用DriverManager.getConnection()方法，我们准备了一个数据库连接。连接准备就绪后，我们使用connection.createStatement()方法创建了一个Statement对象。在创建Statement对象时，我们使用了ResultSet类型TYPE_SCROLL_INSENSITIVE和CONCUR_UPDATABLE，然后使用statement.executeQuery()执行SELECT查询，并将结果存储在结果集中。

我们定义了一个printResultSet()方法，用于打印所有记录。在主方法中，我们使用moveToInsertRow()标记结果集以插入记录。然后，使用updateString()和updateInt()方法添加新值，然后使用insertRow()方法提交更改，从而将记录插入数据库。现在，使用printResultSet()打印所有记录。现在，使用ResultSet.last()方法移动到最后一条记录，并使用ResultSet.deleteRow()方法删除它。然后，使用printResultSet()方法打印所有记录。

将以下示例复制并粘贴到ResultSetExample.java中，编译并运行如下：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.PreparedStatement;

public class ResultSetExample {
   static final String DB_URL = "jdbc:mysql:///TUTORIALSPOINT";
   static final String USER = "guest";
   static final String PASS = "guest123";
   static final String QUERY = "SELECT id, first, last, age FROM Employees";

   public static void printResultSet(ResultSet rs) throws SQLException{
      // Ensure we start with first row
      rs.beforeFirst();
      while(rs.next()){
         // Display values
         System.out.print("ID: " + rs.getInt("id"));
         System.out.print(", Age: " + rs.getInt("age"));
         System.out.print(", First: " + rs.getString("first"));
         System.out.println(", Last: " + rs.getString("last"));
      }
      System.out.println("----------------------------");
   }

   public static void main(String[] args) {
      // Open a connection
      try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
         Statement stmt = conn.createStatement(
            ResultSet.TYPE_SCROLL_INSENSITIVE,
            ResultSet.CONCUR_UPDATABLE);
            ResultSet rs = stmt.executeQuery(QUERY);
         ) {

         System.out.println("Inserting a new record...");
         rs.moveToInsertRow();
         rs.updateString("first","Manoj");
         rs.updateString("last","Jain");
         rs.updateInt("age",40);
         // The code below will insert the row in database
         rs.insertRow();

         System.out.println("List result set showing added row.");
         printResultSet(rs);
         // Deleting the added row.
         rs.last();
         rs.deleteRow();

         System.out.println("List result set showing row after deletion.");

         printResultSet(rs);

      } catch (SQLException e) {
         e.printStackTrace();
      } 
   }
}

输出

现在，我们按如下方式编译上述示例：

C:\>javac ResultSetExample.java
C:\>

运行ResultSetExample时，它会产生以下结果：

C:\>java ResultSetExample
Inserting a new record...
List result set showing added row.
ID: 1, Age: 18, First: Zara, Last: Ali
ID: 2, Age: 25, First: Mahnaz, Last: Fatma
ID: 3, Age: 30, First: Zaid, Last: Khan
ID: 4, Age: 28, First: Sumit, Last: Mittal
ID: 6, Age: 40, First: Manoj, Last: Jain
----------------------------
List result set showing row after deletion.
ID: 1, Age: 18, First: Zara, Last: Ali
ID: 2, Age: 25, First: Mahnaz, Last: Fatma
ID: 3, Age: 30, First: Zaid, Last: Khan
ID: 4, Age: 28, First: Sumit, Last: Mittal
----------------------------

C:\>
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