查询MongoDB中的数组数组

Question

说,我有这样的文件..

"ID" : "fruit1",
"Keys" : [["apple", "carrot", "banana"]]

如何查询Keys ="carrot".以下语法均不起作用.

db.myColl.results.find({ "Keys" : "carrot" });
db.myColl.results.find({ "Keys" : [["carrot"]] });

以下工作,但没有帮助.

db.myColl.results.find({ "Keys" : [["apple", "carrot", "banana]]});

任何指向此查询的指针都会有所帮助.谢谢.

Answer 1

有趣的问题,这将成功

 db.multiArr.find({'Keys':{$elemMatch:{$elemMatch:{$in:['carrot']}}}})

$elemMatch用于检查数组中的元素是否与指定的匹配表达式匹配.所以嵌套$elemMatch将深入嵌套数组

测试数据    

db.multiArr.insert({"ID" : "fruit1","Keys" : [["apple", "carrot", "banana"]]})
db.multiArr.insert({"ID" : "fruit2","Keys" : [["apple", "orange", "banana"]]})


db.multiArr.find({'Keys':{$elemMatch:{$elemMatch:{$in:['carrot']}}}})
{ "_id" : ObjectId("506555212aeb79b5f7374cbf"), "ID" : "fruit1", "Keys" : [ [ "apple", "carrot", "banana" ] ] }

db.multiArr.find({'Keys':{$elemMatch:{$elemMatch:{$in:['banana']}}}})

{ "_id" : ObjectId("506555212aeb79b5f7374cbf"), "ID" : "fruit1", "Keys" : [ [ "apple", "carrot", "banana" ] ] }
{ "_id" : ObjectId("5065587e2aeb79b5f7374cc0"), "ID" : "fruit2", "Keys" : [ [ "apple", "orange", "banana" ] ] }