我有一些文件有一個數組屬性項。 我想獲得n篇文章之間的截距。幾個數組的交集
db.things.insert({name:"A", items:[1,2,3,4,5]})
db.things.insert({name:"B", items:[2,4,6,8]})
db.things.insert({name:"C", items:[1,2]})
db.things.insert({name:"D", items:[5,6]})
db.things.insert({name:"E", items:[9,10]})
db.things.insert({name:"F", items:[1,5]})
數據:
{ "_id" : ObjectId("57974a0d356baff265710a1c"), "name" : "A", "items" : [ 1, 2, 3, 4, 5 ] },
{ "_id" : ObjectId("57974a0d356baff265710a1d"), "name" : "B", "items" : [ 2, 4, 6, 8 ] },
{ "_id" : ObjectId("57974a0d356baff265710a1e"), "name" : "C", "items" : [ 1, 2 ] },
{ "_id" : ObjectId("57974a0d356baff265710a1f"), "name" : "D", "items" : [ 5, 6 ] },
{ "_id" : ObjectId("57974a0d356baff265710a20"), "name" : "E", "items" : [ 9, 10 ] },
{ "_id" : ObjectId("57974a1a356baff265710a21"), "name" : "F", "items" : [ 1, 5 ] }
例如: things.mane.A截距截距things.mane.C things.mane.F:
[1,2,3,4 ,5]截距[1,2]截距[1,5]
必須是:[1]
我認爲這是使用$ setIntersection可行,但我找不到方法。
我可以做到兩個文件,但如何做到更多?
db.things.aggregate({$match:{"name":{$in:["A", "F"]}}},
{$group:{_id:null, "setA":{$first:"$items"}, "setF":{$last:"$items"} } },
{
"$project": {
"set1": 1,
"set2": 1,
"commonToBoth": { "$setIntersection": [ "$setA", "$setF" ] },
"_id": 0
}
}
)
{ "commonToBoth" : [ 5, 1 ] }