与多个字段和mongodb中的where条件不同 [英] distinct with multiple fields and with where condition in mongodb

问题描述

我想写一个与mongodb中的distinct和where等效的查询. sql查询是select DISTINCT key,score from GPC where note="test2" and notetwo = "meet2"

I want to write a query equivalent to distinct and where in mongodb. the sql query is 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"，"score":37}]

[{"key" : "SAGAR33", "score" : 37}]

mongodb中的等效查询是什么.我正在使用猫鼬执行查询.

What is the equivalent query in mongodb. I am using mongoose to execute queries.

推荐答案

您需要使用

You'll need to use the aggregate queries for achieving this. Here's an example that will work in shell (which can be translated to Mongoose easily):

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 }

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