根据以前的值更新列中的所有值

import mysql.connector

# 连接到MySQL数据库
cnx = mysql.connector.connect(user='username', password='password', host='host', database='database')

# 创建游标对象
cursor = cnx.cursor()

# 构建UPDATE语句
update_query = "UPDATE table_name SET column_name = new_value WHERE column_name = old_value"

# 执行UPDATE语句
cursor.execute(update_query)

# 提交事务
cnx.commit()

# 关闭游标和数据库连接
cursor.close()
cnx.close()

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

public class UpdateExample {
    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;

        try {
            // 连接到PostgreSQL数据库
            connection = DriverManager.getConnection("jdbc:postgresql://host:port/database", "username", "password");

            // 创建Statement对象
            statement = connection.createStatement();

            // 构建UPDATE语句
            String updateQuery = "UPDATE table_name SET column_name = new_value WHERE column_name = old_value";

            // 执行UPDATE语句
            statement.executeUpdate(updateQuery);

            // 提交事务
            connection.commit();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭Statement和Connection
            try {
                if (statement != null) {
                    statement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}