node.js oracledb - 使用数组为每组获取一条记录

Posted 2023-03-23

【中文标题】node.js oracledb - 使用数组为每组获取一条记录

【英文标题】：node.js oracledb - Get one record per group with an array

【发布时间】：2016-12-21 20:44:09

【问题描述】：

我正在使用 node.js 和 OracleDB 连接 2 个表，具有一对多的关系。

例如：

RECORDS Table:
RECORD_ID   COMMENTS
1000        Comment 1
1001        Comment 2

设备表：

DEVICE_ID   REF_RECORD_ID   DEVICE_NAME
2000        1000            iPhone 6
2001        1000            iPhone 7
2003        1001            Samsung Galaxy S6
2004        1001            Samsung Galaxy S7

我可以使用

检索联接

SELECT A.RECORD_ID, A.COMMENT, B.DEVICE_ID, B.DEVICE_NAME FROM RECORDS A, DEVICES B WHERE A.RECORD_ID = B.REF_RECORD_ID;

当前结果：

[
    RECORD_ID: 1000, COMMENT: "Comment 1", DEVICE_ID: 2000, DEVICE_NAME: "iPhone 6"
,

    RECORD_ID: 1000, COMMENT: "Comment 1", DEVICE_ID: 2001, DEVICE_NAME: "iPhone 7"
,

    RECORD_ID: 1001, COMMENT: "Comment 2", DEVICE_ID: 2003, DEVICE_NAME: "Samsung Galaxy S6"
,

    RECORD_ID: 1001, COMMENT: "Comment 2", DEVICE_ID: 2004, DEVICE_NAME: "Samsung Galaxy S7"
]

但我想要如下所示的结果：

[
    RECORD_ID: 1000, COMMENT: "Comment 1",
    DEVICES: [ DEVICE_ID: 2000, DEVICE_NAME: "iPhone 6" ,  DEVICE_ID: 2001, DEVICE_NAME: "iPhone 7" ]
,

    RECORD_ID: 1001, COMMENT: "Comment 2",
    DEVICES: [ DEVICE_ID: 2003, DEVICE_NAME: "Samsung Galaxy S6" ,  DEVICE_ID: 2004, DEVICE_NAME: "Samsung Galaxy S7" ]
]

有没有更好的方法来做到这一点，而不是循环遍历对象数组，然后找到重复的 RECORD_ID 并创建一个数组来推送子项？

【参考方案1】：

当支持嵌套游标表达式时，您指定的输出可以直接完成。你可以看到其他人在这里寻找同样的东西： https://github.com/oracle/node-oracledb/issues/565

同时，这里有一些代码示例，一旦您获得结果集，就可以在 Node.js 中执行此操作：

var resultRowsIdx;
var resultRows = [
    RECORD_ID: 1000, COMMENT: "Comment 1", DEVICE_ID: 2000, DEVICE_NAME: "iPhone 6"
,

    RECORD_ID: 1000, COMMENT: "Comment 1", DEVICE_ID: 2001, DEVICE_NAME: "iPhone 7"
,

    RECORD_ID: 1001, COMMENT: "Comment 2", DEVICE_ID: 2003, DEVICE_NAME: "Samsung Galaxy S6"
,

    RECORD_ID: 1001, COMMENT: "Comment 2", DEVICE_ID: 2004, DEVICE_NAME: "Samsung Galaxy S7"
];
var records = [];
var recordsMap = ;
var currentRecordId;

for (resultRowsIdx = 0; resultRowsIdx < resultRows.length; resultRowsIdx += 1) 
  currentRecordId = resultRows[resultRowsIdx].RECORD_ID;

  if (!recordsMap[currentRecordId]) 
    recordsMap[currentRecordId] = ;
    recordsMap[currentRecordId].RECORD_ID = currentRecordId;
    recordsMap[currentRecordId].COMMENT = resultRows[resultRowsIdx].COMMENT;
    recordsMap[currentRecordId].DEVICES = [];

    records.push(recordsMap[currentRecordId]);
  

  recordsMap[currentRecordId].DEVICES.push(
    DEVICE_ID: resultRows[resultRowsIdx].DEVICE_ID,
    DEVICE_NAME: resultRows[resultRowsIdx].DEVICE_NAME
  );


console.log(records);