mongodb - MongoDB get attribute from array inside another array

Question

Series is one document. It has an array of series inside it (in this case it has 'Revenge' and 'Raines'). Each series has a cast array with names. And I need a query to get those names.

Who know how can I get a list of all the names from both cast arrays?

My best approach was this query db.series.find( {}, { _id: 0, cast: 1 } ) where a get a cursor with the two cast json arrays.

{ series:
[ 
{ 
  name: 'Revenge',
  user_rating: 7.9,
  duration: 44,
  genres: [ ' Drama', ' Mystery', ' Thriller' ],
  year_start: '2011',
  year_end: '',
  cast: 
   [ { name: 'Madeleine Stowe' },
     { name: 'Emily VanCamp' },
     { name: 'Gabriel Mann' },
     { name: 'Nick Wechsler' },
     { name: 'Henry Czerny' },
     { name: 'Joshua Bowman' },
     { name: 'Christa B. Allen' },
     { name: 'Ashley Madekwe' },
     { name: 'Connor Paolo' },
     { name: 'Barry Sloane' },
     { name: 'Margarita Levieva' } ],
  seasons: [ { number: '3' }, { number: '2' }, { number: '1' } ]

},
{
name: 'Raines',
user_rating: 7.4,
duration: 45,
genres: [ ' Crime', ' Drama' ],
year_start: '2007',
year_end: '',
cast: 
    [ { name: 'Jeff Goldblum' },
     { name: 'Matt Craven' },
     { name: 'Nicole Sullivan' },
     { name: 'Linda Park' },
     { name: 'Dov Davidoff' },
     { name: 'Malik Yoba' },
     { name: 'Madeleine Stowe' } ],
seasons: [ { number: '1' } ] 

}
]
}

I need an output like this:

I need this:
         { name: 'Madeleine Stowe' },
     { name: 'Emily VanCamp' },
     { name: 'Gabriel Mann' },
     { name: 'Nick Wechsler' },
     { name: 'Henry Czerny' },
     { name: 'Joshua Bowman' },
     { name: 'Christa B. Allen' },
     { name: 'Ashley Madekwe' },
     { name: 'Connor Paolo' },
     { name: 'Barry Sloane' },
     { name: 'Margarita Levieva' },
         { name: 'Jeff Goldblum' },
     { name: 'Matt Craven' },
     { name: 'Nicole Sullivan' },
     { name: 'Linda Park' },
     { name: 'Dov Davidoff' },
     { name: 'Malik Yoba' },
     { name: 'Madeleine Stowe' }

Answer 1

您可以为此使用聚合框架：

db.series.aggregate( { $unwind : "$series" },
                     { $unwind : "$series.cast" },
                     { $group  : { _id  : "$_id",
                                   cast : {$push:"$series.cast}
                                 }
                     }
);

如果您想将多个演员外观合并为一个，请替换$push为$addToSet.