title: jq - error when merging two JSON files "cannot be multiplied"
body: <p>I have two files containing some JSON.</p>
  
  <p>File1 - some values can be a string, some might be null, VolumeId is always set.</p>
  
  <pre><code>[
    {
      "VolumeId": "vol-xxxxxxx1",
      "Tag1": "Tag1Value",
      "Tag2": "Tag2Value",
      "Tag3": "Tag3Value",
      "Tag4": "Tag4Value",
      "Tag5": "Tag5Value",
      "Tag6": "Tag6Value"
    },
    {
      "VolumeId": "vol-xxxxxxx2",
      "Tag1": "Tag1Value",
      "Tag2": "null",
      "Tag3": "null",
      "Tag4": "Tag4Value",
      "Tag5": "null",
      "Tag6": "Tag6Value"
    },
    {
      "VolumeId": "vol-xxxxxxx3",
      "Tag1": "null",
      "Tag2": "null",
      "Tag3": "null",
      "Tag4": "null",
      "Tag5": "null",
      "Tag6": "null"
    }
  ]
  </code></pre>
  
  <p>File2 - VolumeId will always match as those in File1, and Tag7 may or may not be null.</p>
  
  <pre><code>[
    {
      "VolumeId": "vol-xxxxxxx1",
      "Tag7": "Tag7Value"
    },
    {
      "VolumeId": "vol-xxxxxxx2",
      "Tag7": "Tag7Value"
    },
    {
      "VolumeId": "vol-xxxxxxx3",
      "Tag7": "null"
    }
  ]
  </code></pre>
  
  <p>I need to combine these into one JSON array:</p>
  
  <pre><code>[
    {
      "VolumeId": "vol-xxxxxxx1",
      "Tag1": "Tag1Value",
      "Tag2": "Tag2Value",
      "Tag3": "Tag3Value",
      "Tag4": "Tag4Value",
      "Tag5": "Tag5Value",
      "Tag6": "Tag6Value",
      "Tag7": "Tag7Value"
    },
    {
      "VolumeId": "vol-xxxxxxx2",
      "Tag1": "Tag1Value",
      "Tag2": "null",
      "Tag3": "null",
      "Tag4": "Tag4Value",
      "Tag5": "null",
      "Tag6": "Tag6Value",
      "Tag7": "Tag7Value"
    },
    {
      "VolumeId": "vol-xxxxxxx3",
      "Tag1": "null",
      "Tag2": "null",
      "Tag3": "null",
      "Tag4": "null",
      "Tag5": "null",
      "Tag6": "null",
      "Tag7": "null"
    }
  ]
  </code></pre>
  
  <p>I get an error when trying to use the below command:</p>
  
  <pre><code>jq -s '.[0] * .[1]' /path/to/file1 /path/to/file2
  array ([{"VolumeId...) and array ([{"VolumeId...) cannot be multiplied
  </code></pre>
  
  <p>Any help is appreciated.</p>