Java Mysql 简明教程

Java & MySQL - Updating a ResultSet

ResultSet 接口包含一组用于更新结果集数据的更新方法。

与 get 方法类似,针对每种数据类型有两种更新方法:

  1. 一个接受列名称。

  2. 一个接受列索引。

例如,要更新结果集当前行的 String 列,将使用以下任一 updateString() 方法:

S.N.

Methods & Description

1

*public void updateString(int columnIndex, String s) throws SQLException*将指定列中的 String 更改为 s 的值。

2

*public void updateString(String columnName, String s) throws SQLException*与上一个方法类似,只是通过名称而不是索引指定列。

有用于八种原始数据类型以及 java.sql 包中的 String、Object、URL 和 SQL 数据类型的更新方法。

更新结果集中的行将更改 ResultSet 对象中当前行的列,但不会更改底层数据库中的内容。要更新对数据库中行的更改,需要调用以下任一方法。

S.N.

Methods & Description

1

*public void updateRow()*通过更新数据库中相应的行来更新当前行。

2

*public void deleteRow()*从数据库中删除当前行

3

*public void refreshRow()*刷新结果集中的数据以反映数据库中的任何近期更改。

4

*public void cancelRowUpdates()*取消对当前行进行的任何更新。

5

*public void insertRow()*将行插入数据库。只能在游标指向插入行时调用此方法。

以下是 Result Set 教程中描述的 ResultSet.CONCUR_UPDATABLEResultSet.TYPE_SCROLL_INSENSITIVE 示例。此示例将解释表上的 INSERT、UPDATE 和 DELETE 操作。

需要注意的是,您正在处理的表应该正确设置了主键。让我们首先更新参照表。

删除表并按照如下方法重新创建表 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>

Create Data Records

最后,在 Employee 表中创建一些记录,如下所示 −

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>

将以下示例复制并粘贴到 TestApplication.java 中,如下进行编译和运行:

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

public class TestApplication {
   static final String DB_URL = "jdbc:mysql://localhost/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();
      }
   }
}

现在让我们如下编译上述示例:

C:\>javac TestApplication.java
C:\>

运行 TestApplication 时,它会生成以下结果:

C:\>java TestApplication
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:\>