与多个字段不同,以及mongodb中的where条件

Question

我想查询相当于写入distinct和where在mongodb.sql查询是 select DISTINCT key,score from GPC where note="test2" and notetwo = "meet2"

{ "_id" : ObjectId("4dc86fef6a0aa8513ab5f21c"), "key" : "SAGAR","score" : 16, "note" : "test1", "notetwo" : "meet1" } 
{ "_id" : ObjectId("4dc86ffd6a0aa8513ab5f21d"), "key" : "SAGAR456", "score" : 17, "note" : "testjh1", "notetwo" : "meetjh1" } 
{ "_id" : ObjectId("4dc8700b6a0aa8513ab5f21e"), "key" : "SAGAR33", "score" : 37, "note" : "test2", "notetwo" : "meet2" } 
{ "_id" : ObjectId("4dc871686a0aa8513ab5f21f"), "key" : "SAGAR33", "score" : 37, "note" : "test2", "notetwo" : "meet2" } 
{ "_id" : ObjectId("4dc871696a0aa8513ab5f220"), "key" : "SAGAR33", "score" : 37, "note" : "test2", "notetwo" : "meet2" } 
{ "_id" : ObjectId("4dc8716c6a0aa8513ab5f221"), "key" : "SAGAR456", "score" : 17, "note" : "testjh1", "notetwo" : "meetjh1" } 

查询的预期结果是

[{"key":"SAGAR33","得分":37}]

什么是等效查询mongodb.我正在使用mongoose来执行查询.

Answer 1

您需要使用aggregate查询来实现此目的.这是一个可以在shell中工作的例子(可以很容易地翻译成Mongoose):

db.gpc.aggregate([
    // your where clause: note="test2" and notetwo = "meet2"
    {"$match" : {note:"test2", notetwo:"meet2"}}, 
    // group by key, score to get distinct
    {"$group" : {_id : {key:"$key", score:"$score"}}}, 
    // Clean up the output
    {"$project" : {_id:0, key:"$_id.key", score:"$_id.score"}}
])

输出:

{ "result" : [ { "key" : "SAGAR33", "score" : 37 } ], "ok" : 1 }