從JSON對象的數組MongoDB中

Question

提取值

考慮一下：

{ 
    "movies": [ 
    { 
     "title": "Star Wars", 
     "year": 1977, 
     "director": "George Lucas" 
    }, 
    { 
     "title": "The Empire Strikes Back", 
     "year": 1980, 
     "director": "Irvin Kershner" 
    }, 
    { 
     "title": "Return of the Jedi", 
     "year": 1983, 
     "director": "Richard Marquand" 
    }, 
    { 
     "title": "The Phantom Menace", 
     "year": 1999, 
     "director": "George Lucas" 
    }, 
    { 
     "title": "Attack of the Clones", 
     "year": 2002, 
     "director": "George Lucas" 
    }, 
    { 
     "title": "Revenge of the Sith", 
     "year": 2005, 
     "director": "George Lucas" 
    }, 
    { 
     "title": "The Force Awakens", 
     "year": 2015, 
     "director": "J.J. Abrams" 
    } 
    ] 
} 

我試圖拔出由喬治·盧卡斯執導的所有電影。這是我曾嘗試和返回的所有項目：

db.movies.find({"movies.director" : "George Lucas"}).pretty() 

而且這導致一個錯誤：

db.movies.find({"$pull" : {"movies.director" : "George Lucas"}}).pretty() 

請讓我知道如何查詢數據庫，檢索只有電影，其中導演鑰匙有「喬治盧卡斯」作爲價值。

Answer 1

您需要使用聚合框架：

db.movies.aggregate([ 
{ 
    $unwind : "$movies" 
}, 
{ 
    $match : { 
     "movies.director" : "George Lucas" 
    } 
}, 
{ 
    $project : { 
     _id : 0, 
     movies : 1 
    } 
} 
])