https://stackoverflow.com/questions/69137721/how-to-merge-and-aggregate-values-in-2-json-files-using-jq

gistfile1.txt

$ xidel -se 'json-doc("Input1.json")(),json-doc("Input2.json")()'
$ xidel -se '
  json-doc("Input1.json")(),
  json-doc("Input2.json")()
'
{
  "A": "Name 1",
  "B": "1.1",
  "C": "2"
}
{
  "A": "Name 2",
  "B": "3.2",
  "C": "4"
}
{
  "A": "Name 2",
  "B": "5",
  "C": "6"
}
{
  "A": "Name 3",
  "B": "7",
  "C": "8"
}

$ xidel -se 'let $src:=(json-doc("Input1.json")(),json-doc("Input2.json")()) return $src/A'
$ xidel -se '
  let $src:=(
    json-doc("Input1.json")(),json-doc("Input2.json")()
  )
  return
  $src/A
'
Name 1
Name 2
Name 2
Name 3

$ xidel -se 'let $src:=(json-doc("Input1.json")(),json-doc("Input2.json")()) return distinct-values($src/A)'
$ xidel -se '
  let $src:=(
    json-doc("Input1.json")(),
    json-doc("Input2.json")()
  )
  return
  distinct-values($src/A)
'
Name 1
Name 2
Name 3

$ xidel -se 'let $src:=(json-doc("Input1.json")(),json-doc("Input2.json")()) for $name at $i in distinct-values($src/A) return ($i,$src[A=$name])'
$ xidel -se '
  let $src:=(
    json-doc("Input1.json")(),
    json-doc("Input2.json")()
  )
  for $name at $i in distinct-values($src/A)
  return
  ($i,$src[A=$name])
'
1
{
  "A": "Name 1",
  "B": "1.1",
  "C": "2"
}
2
{
  "A": "Name 2",
  "B": "3.2",
  "C": "4"
}
{
  "A": "Name 2",
  "B": "5",
  "C": "6"
}
3
{
  "A": "Name 3",
  "B": "7",
  "C": "8"
}

$ xidel -se 'let $src:=(json-doc("Input1.json")(),json-doc("Input2.json")()) for $name in distinct-values($src/A) let $obj:=$src[A=$name] return if (count($obj) gt 1) then map:merge(for $key in map:keys($obj[1]) return map:entry($key,if ($obj[1]($key) castable as decimal) then string($obj[1]($key) + $obj[2]($key)) else $obj[1]($key))) else $obj'
$ xidel -se '
  let $src:=(
    json-doc("Input1.json")(),
    json-doc("Input2.json")()
  )
  for $name in distinct-values($src/A)
  let $obj:=$src[A=$name]
  return
  if (count($obj) gt 1)
  then map:merge(
    for $key in map:keys($obj[1]) return
    map:entry(
      $key,
      if ($obj[1]($key) castable as decimal)
      then string($obj[1]($key) + $obj[2]($key))
      else $obj[1]($key)
    )
  )
  else $obj
'
{
  "A": "Name 1",
  "B": "1.1",
  "C": "2"
}
{
  "A": "Name 2",
  "B": "8.2",
  "C": "10"
}
{
  "A": "Name 3",
  "B": "7",
  "C": "8"
}

$ xidel -se 'array{let $src:=(json-doc("Input1.json")(),json-doc("Input2.json")()) for $name in distinct-values($src/A) let $obj:=$src[A=$name] return if (count($obj) gt 1) then map:merge(for $key in map:keys($obj[1]) return map:entry($key,if ($obj[1]($key) castable as decimal) then string($obj[1]($key) + $obj[2]($key)) else $obj[1]($key))) else $obj}'
$ xidel -se '
  array{
    let $src:=(
      json-doc("Input1.json")(),
      json-doc("Input2.json")()
    )
    for $name in distinct-values($src/A)
    let $obj:=$src[A=$name]
    return
    if (count($obj) gt 1)
    then map:merge(
      for $key in map:keys($obj[1]) return
      map:entry(
        $key,
        if ($obj[1]($key) castable as decimal)
        then string($obj[1]($key) + $obj[2]($key))
        else $obj[1]($key)
      )
    )
    else $obj
  }
'
[
  {
    "A": "Name 1",
    "B": "1.1",
    "C": "2"
  },
  {
    "A": "Name 2",
    "B": "8.2",
    "C": "10"
  },
  {
    "A": "Name 3",
    "B": "7",
    "C": "8"
  }
]