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Legal Studies如何使用 JDBC API 来更新数据库表中记录的内容？
A. 可使用 UPDATE 查询来更新/修改表中记录的现有内容。使用此功能可更新表的所有记录或特定记录。
语法
UPDATE table_name SET column1 = value1, column2 = value2...., columnN = valueN WHERE [condition];
要使用 JDBC API 更新表中记录的内容，需要
注册驱动程序：使用 DriverManager 类的 registerDriver() 方法注册驱动程序类。将其中的驱动程序类名作为参数传递。
建立连接：使用 DriverManager 类中的 getConnection() 方法连接数据库。将其中的 URL（字符串）、用户名（字符串）、密码（字符串）作为参数传递。
创建语句：使用 Connection 接口中的 createStatement() 方法创建一个 Statement 对象。
执行查询：使用 Statement 接口中的 executeUpdate() 方法执行查询。
示例
假设我们在 MySQL 中名为 mydatabase 的数据库中有一张名为 customers 的表，其中有 12 条记录：
+----+-----------+------+---------+----------------+ | ID | NAME | AGE | SALARY | ADDRESS | +----+-----------+------+---------+----------------+ | 1 | Amit | 25 | 3000.00 | Hyderabad | | 2 | Kalyan | 27 | 4000.00 | Vishakhapatnam | | 3 | Renuka | 30 | 5000.00 | Delhi | | 4 | Archana | 24 | 1500.00 | Mumbai | | 5 | Koushik | 30 | 9000.00 | Kota | | 6 | Hardik | 45 | 6400.00 | Bhopal | | 7 | Trupthi | 33 | 4360.00 | Ahmedabad | | 8 | Mithili | 26 | 4100.00 | Vijayawada | | 9 | Maneesh | 39 | 4000.00 | Hyderabad | | 10 | Rajaneesh | 30 | 6400.00 | Delhi | | 11 | Komal | 29 | 8000.00 | Ahmedabad | | 12 | Manyata | 25 | 5000.00 | Vijayawada | +----+-----------+------+---------+----------------+
以下 JDBC 程序建立与 MySQL 的连接，并将 id 为 4、5、6 和 7 的客户地址更新为德里，并在更新后检索并显示表的内容。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class UpdateRecordsExample {
public static void main(String args[]) throws SQLException {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String mysqlUrl = "jdbc:mysql:///MyDatabase";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("Connection established......");
//Creating the Statement
Statement stmt = con.createStatement();
//Query to update records
String query = "update customers set address = 'Delhi' where ID in (4, 5, 6, 7 )";
//Executing the query
int i = stmt.executeUpdate(query);
System.out.println("Rows updated: "+i);
System.out.println("Contents of the customers table after updating the records: ");
//Retrieving data
ResultSet rs = stmt.executeQuery("Select * from customers");
while(rs.next()) {
System.out.print("ID: "+rs.getInt("ID")+", ");
System.out.print("Name: "+rs.getString("Name")+", ");
System.out.print("Age: "+rs.getInt("Age")+", ");
System.out.print("Salary: "+rs.getInt("Salary")+", ");
System.out.print("Address: "+rs.getString("Address"));
System.out.println();
}
}
}输出
Connection established...... Rows updated: 4 Contents of the customers table after updating the records: ID: 1, Name: Amit, Age: 25, Salary: 3000, Address: Hyderabad ID: 2, Name: Kalyan, Age: 27, Salary: 4000, Address: Vishakhapatnam ID: 3, Name: Renuka, Age: 30, Salary: 5000, Address: Delhi ID: 4, Name: Archana, Age: 24, Salary: 1500, Address: Delhi ID: 5, Name: Koushik, Age: 30, Salary: 9000, Address: Delhi ID: 6, Name: Hardik, Age: 45, Salary: 6400, Address: Delhi ID: 7, Name: Trupthi, Age: 33, Salary: 4360, Address: Delhi ID: 8, Name: Mithili, Age: 26, Salary: 4100, Address: Vijayawada ID: 9, Name: Maneesh, Age: 39, Salary: 4000, Address: Hyderabad ID: 10, Name: Rajaneesh, Age: 30, Salary: 6400, Address: Delhi ID: 11, Name: Komal, Age: 8000, Salary: 29, Address: Ahmedabad ID: 12, Name: Manyata, Age: 5000, Salary: 25, Address: Vijayawada
更新于: 2019 年 7 月 30 日
175 次浏览
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