如何獲取MongoDB中的特定字段只有沒有鍵的值？

我的數據集如下：如何獲取MongoDB中的特定字段只有沒有鍵的值？

{ "_id" : "EVNQUERY-k9Uoo74Q3WcdmU", "event_data" : "{\"data\":\"helo\"}", "event_name" : "onOemPushAlert", "timestamp_start" : 1452678481433, "timestamp_end" : 1452678481433, "sender" : "USR-ADMIN", "status" : "pending", "query" : { "user" : { "and" : [ { "email" : { "eq" : "" } } ] } }, "updated_on" : ISODate("2016-01-13T09:48:01.459Z"), "created_on" : ISODate("2016-01-13T09:48:01.459Z") } 

{ "_id" : "EVNQUERY-yAKmrbzs2JeaUY", "event_data" : "{\"data\":\"ji\"}", "event_name" : "onOemPushAlert", "timestamp_start" : 1452681060159, "timestamp_end" : 1452681060159, "sender" : "USR-ADMIN", "status" : "pending", "query" : { "user" : { "@@@[email protected]@@" : [ { "email" : { "eq" : "" } } ] } }, "updated_on" : ISODate("2016-01-13T10:31:00.223Z"), "created_on" : ISODate("2016-01-13T10:31:00.223Z") } 

{ "_id" : "EVNQUERY-0NeCstt2eJchDZ", "event_data" : "{\"data\":\"hyg\"}", "event_name" : "onOemPushAlert", "timestamp_start" : 1452681073882, "timestamp_end" : 1452681073882, "sender" : "USR-ADMIN", "status" : "pending", "query" : { "user" : { "@@@[email protected]@@" : [ { "email" : { "eq" : "" } } ] } }, "updated_on" : ISODate("2016-01-13T10:31:13.897Z"), "created_on" : ISODate("2016-01-13T10:31:13.897Z") }

和我運行下面的查詢

db.eventqueries.find({},{_id:1})

，但它給我

{ "_id" : "EVNQUERY-k9Uoo74Q3WcdmU" } 
{ "_id" : "EVNQUERY-yAKmrbzs2JeaUY" } 
{ "_id" : "EVNQUERY-0NeCstt2eJchDZ" }

，但我想要的是

["EVNQUERY-k9Uoo74Q3WcdmU", "EVNQUERY-yAKmrbzs2JeaUY", "EVNQUERY-0NeCstt2eJchDZ"]

來源

2016-01-13 Er. Mohit Agrawal

在收集執行鍼對_id領域distinct()查詢：

db.eventqueries.distinct("_id")

在node.js的驅動程序運行distinct()命令這將有結果的回調：

collection.distinct("_id", function(err, docs) { 
    if (err) { /* handle error */ }; 
    console.log(docs); 
});

來源

2016-01-13 11:16:59 chridam

你可以使用聚合來實現你想要的。你可以試試這個

db.eventqueries.aggregate([ 
    { 
     $group : { 
      keys : { $push : "_id" } 
     } 
    } 
])

來源

2016-01-13 11:17:03

如何獲取MongoDB中的特定字段只有沒有鍵的值？

回答

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