如何使用jq在特定字段上联接JSON对象? [英] How to join JSON objects on particular fields using jq?

问题描述

我具有以下JSON结构:

I have following JSON structure:

{
  "Reservations": [
    {
      "Id": "R-1",
      "CustomerId": "1"
    },
    {
      "Id": "R-2",
      "CustomerId": "2"
    }
  ],
  "Customers": [
    {
      "Id": "1",
      "Name": "customer 1"
    },
    {
      "Id": "2",
      "Name": "customer 2"
    },
    {
      "Id": "3",
      "Name": "customer 3"
    }
  ]
}

我想与 Customers 一起加入 Reservations ，并获得如下信息:

I want to join Reservations with Customers and get something like this:

{
  "ReservationId": "R-1",
  "CustomerName": "customer 1"
}
{
  "ReservationId": "R-2",
  "CustomerName": "customer 2"
}

我已经广泛地使用过 jq ，尝试使用多个用逗号分隔的过滤器，尝试使用变量，阅读文档，但是使用 jq似乎无法完成如此简单的任务.或者，我想念什么吗?

I've played with jq extensively, tried using multiple filters separated by comma, tried using variables, read the docs, but it seems like doing such a simple tasks is impossible with jq. Or, am I missing something?

推荐答案

这是使用 INDEX/2 的简单解决方案:

Here's a simple solution using INDEX/2:

INDEX(.Customers[]; .Id) as $c
| .Reservations[]
| { ReservationId: .Id,
    CustomerName: $c[.CustomerId].Name }

如果您的jq没有 INDEX/2 ，那么现在是升级的好时机；否则，您可以从 https://复制并粘贴其定义github.com/stedolan/jq/blob/master/src/builtin.jq ，或者您可以使用如下定义的 INDEX/3 .

If your jq does not have INDEX/2 then now would be a good time to upgrade; otherwise, you can copy-and-paste its def from https://github.com/stedolan/jq/blob/master/src/builtin.jq, or you could use INDEX/3 as defined below.

def INDEX(s; k; v):
  reduce s as $x ({}; .[$x|k] = ($x|v));

INDEX(.Customers[]; .Id; .Name) as $c
| .Reservations[]
| { ReservationId: .Id,
    CustomerName: $c[.CustomerId] }

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