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

/**
 * 只读探针：执行一条查询并把结果按列打印出来（用于核对服务器上的数据现状）。
 *
 * <p>用法：java Query &lt;jdbc-url&gt; "select ..."
 */
public class Query {

    public static void main(String[] args) throws Exception {
        try (Connection connection = DriverManager.getConnection(args[0], "root", "123456");
             Statement statement = connection.createStatement();
             ResultSet rows = statement.executeQuery(args[1])) {
            ResultSetMetaData meta = rows.getMetaData();
            int columns = meta.getColumnCount();
            StringBuilder header = new StringBuilder();
            for (int index = 1; index <= columns; index++) header.append(meta.getColumnLabel(index)).append(" | ");
            System.out.println(header);
            while (rows.next()) {
                StringBuilder line = new StringBuilder();
                for (int index = 1; index <= columns; index++) {
                    Object value = rows.getObject(index);
                    line.append(value == null ? "NULL" : String.valueOf(value)).append(" | ");
                }
                System.out.println(line);
            }
        }
    }
}