步骤 4：查询分类账中的表

查询表格

1. 使用以下程序（FindVehicles.ts），以查询分类账中某人名下注册的所有车辆。

   /*
    * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
    * SPDX-License-Identifier: MIT-0
    *
    * Permission is hereby granted, free of charge, to any person obtaining a copy of this
    * software and associated documentation files (the "Software"), to deal in the Software
    * without restriction, including without limitation the rights to use, copy, modify,
    * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
    * permit persons to whom the Software is furnished to do so.
    *
    * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
    * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
    * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
    * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
    * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    */
   
   import { QldbDriver, Result, TransactionExecutor } from "amazon-qldb-driver-nodejs";
   import { dom } from "ion-js";
   
   import { getQldbDriver } from "./ConnectToLedger";
   import { PERSON } from "./model/SampleData";
   import { PERSON_TABLE_NAME } from "./qldb/Constants";
   import { error, log } from "./qldb/LogUtil";
   import { getDocumentId } from "./qldb/Util";
   import { prettyPrintResultList } from "./ScanTable";
   
   /**
    * Query 'Vehicle' and 'VehicleRegistration' tables using a unique document ID in one transaction.
    * @param txn The {@linkcode TransactionExecutor} for lambda execute.
    * @param govId The owner's government ID.
    * @returns Promise which fulfills with void.
    */
   async function findVehiclesForOwner(txn: TransactionExecutor, govId: string): Promise<void> {
       const documentId: string = await getDocumentId(txn, PERSON_TABLE_NAME, "GovId", govId);
       const query: string = "SELECT Vehicle FROM Vehicle INNER JOIN VehicleRegistration AS r " +
                           "ON Vehicle.VIN = r.VIN WHERE r.Owners.PrimaryOwner.PersonId = ?";
   
       await txn.execute(query, documentId).then((result: Result) => {
           const resultList: dom.Value[] = result.getResultList();
           log(`List of vehicles for owner with GovId: ${govId}`);
           prettyPrintResultList(resultList);
       });
   }
   
   /**
    * Find all vehicles registered under a person.
    * @returns Promise which fulfills with void.
    */
   const main = async function(): Promise<void> {
       try {
           const qldbDriver: QldbDriver = getQldbDriver();
           await qldbDriver.executeLambda(async (txn: TransactionExecutor) => {
               await findVehiclesForOwner(txn, PERSON[0].GovId);
           });
       } catch (e) {
           error(`Error getting vehicles for owner: ${e}`);
       }
   }
   
   if (require.main === module) {
       main();
   }

   注意

   首先，该程序在 Person 表格中查询文档GovId LEWISR261LL，以获取其id元数据字段。

   然后，它使用文档id，通过PrimaryOwner.PersonId作为外键查询VehicleRegistration表。它还结合VIN字段上的Vehicle表的VehicleRegistration。

2. 要运行编译后的程序，请输入以下命令。

   node dist/FindVehicles.js