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Legal Studies如何使用 JDBC API 來更新資料庫表中記錄的內容？
A. 可使用 UPDATE 查詢來更新/修改表中記錄的現有內容。使用此功能可更新表的所有記錄或特定記錄。
語法
UPDATE table_name SET column1 = value1, column2 = value2...., columnN = valueN WHERE [condition];
要使用 JDBC API 更新表中記錄的內容，需要
註冊驅動程式：使用 DriverManager 類的 registerDriver() 方法註冊驅動程式類。將其中的驅動程式類名作為引數傳遞。
建立連線：使用 DriverManager 類中的 getConnection() 方法連線資料庫。將其中的 URL（字串）、使用者名稱（字串）、密碼（字串）作為引數傳遞。
建立語句：使用 Connection 介面中的 createStatement() 方法建立一個 Statement 物件。
執行查詢：使用 Statement 介面中的 executeUpdate() 方法執行查詢。
示例
假設我們在 MySQL 中名為 mydatabase 的資料庫中有一張名為 customers 的表，其中有 12 條記錄：
+----+-----------+------+---------+----------------+ | 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 程式建立與 MySQL 的連線，並將 id 為 4、5、6 和 7 的客戶地址更新為德里，並在更新後檢索並顯示錶的內容。
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();
}
}
}輸出
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
更新於: 2019 年 7 月 30 日
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