如何返回表的列名？

SELECT column_name
FROM information_schema.columns
WHERE table_name = 'your_table_name';

db.your_collection_name.aggregate([
  {
    $project: {
      _id: 0,
      fieldNames: { $objectToArray: '$$ROOT' }
    }
  },
  {
    $unwind: '$fieldNames'
  },
  {
    $group: {
      _id: null,
      fieldNames: { $addToSet: '$fieldNames.k' }
    }
  },
  {
    $project: {
      _id: 0,
      fieldNames: 1
    }
  }
]);