Assigning data

Let can be used to store values in variables or define subqueries to be used in other queries (see joins)

Let for storing values

1. Let allows you to define variables, but the variabl assingment can be done only once

let a = [1, 2, 3]  // initial assignment

// parsing error, variable 'a' is assigned multiple times
//LET a= PUSH(a, 4) 

let b = push(a, 4) // allowed, result: [1, 2, 3, 4]
let c = push(b, 5) // allowed, result: [1, 2, 3, 4, 5]

return {a:a,b:b,c:c}

2. The expected output is as follows:

  [
    {
      "a": [
        1,
        2,
        3
      ],
      "b": [
        1,
        2,
        3,
        4
      ],
      "c": [
        1,
        2,
        3,
        4,
        5
      ]
    }
  ]

3. You can also use LET to assign to a variable and sort on a specific field

//Ingore the schedule of flight, only consider unique routes (irrespective of time/schedule)
for flight in flights
 LET route= {
  _from: flight._from,
  _to: flight._to,
  UniqueCarrier: flight.UniqueCarrier,
  Distance: flight.Distance
  }
 
sort route.Distance desc
 
return distinct route

4. You should see the following results (snippet):

  [
    {
      "_from": "airports/HNL",
      "_to": "airports/EWR",
      "UniqueCarrier": "CO",
      "Distance": 4962
    },
    {
      "_from": "airports/EWR",
      "_to": "airports/HNL",
      "UniqueCarrier": "CO",
      "Distance": 4962
    },
    {
      "_from": "airports/ATL",
      "_to": "airports/HNL",
      "UniqueCarrier": "DL",
      "Distance": 4502
    },
    {
      "_from": "airports/HNL",
      "_to": "airports/ATL",
      "UniqueCarrier": "DL",
      "Distance": 4502
    },
    {
      "_from": "airports/HNL",
      "_to": "airports/ORD",
      "UniqueCarrier": "UA",
      "Distance": 4243
    },
    {
      "_from": "airports/HNL",
      "_to": "airports/ORD",
      "UniqueCarrier": "AA",
      "Distance": 4243
    },
    {
      "_from": "airports/ORD",
      "_to": "airports/HNL",
      "UniqueCarrier": "AA",
      "Distance": 4243
    },
    ...

 

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