MongoDB的聚集匹配的ID和组

Question

IVE嗨创建MongoDB中一个数据库，并创建插入即时通讯目前只是在学习如何使用聚合和我奋力用一点点，并不会寻找一些帮助，为什么我的命令返回任何结果。这里是插入：

db.transaction.insert({"EmpId":"005","transaction":[{"TID":"O02","Date":"3/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Steam Gift Card","amount":25}], "Total" : "84.99"}); 
db.transaction.insert({"EmpId":"001","transaction":[{"TID":"O03","Date":"3/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Playstation Controller","amount":25}], "Total" : "84.99"}); 
db.transaction.insert({"EmpId":"003","transaction":[{"TID":"O04","Date":"3/27/2017","product":[{"product_name":"Unchartered 2","quantity":1,"amount":49.99}]}], "Total" : "49.99"}); 
db.transaction.insert({"EmpId":"003","transaction":[{"TID":"O05","Date":"3/27/2017","product":[{"product_name":"Playstation 4","quantity":1,"amount":359.99}]},{"product_name":"Battlefield 2","amount":49.99}], "Total" : "409.98"}); 
db.transaction.insert({"EmpId":"004","transaction":[{"TID":"O06","Date":"4/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Steam Gift Card","amount":50}], "Total" : "109.99"}); 
db.transaction.insert({"EmpId":"001","transaction":[{"TID":"O07","Date":"4/27/2017","product":[{"product_name":"CSGO","quantity":1,"amount":13.99}]},{"product_name":"GTA4","amount": 39.99}], "Total" : "53.98"}); 
db.transaction.insert({"EmpId":"002","transaction":[{"TID":"O08","Date":"5/27/2017","product":[{"product_name":"Sparta","quantity":3,"amount":17.99}]},{"product_name":"Action Figures","amount": 9.99}], "Total" : "63.96"}); 
db.transaction.insert({"EmpId":"005","transaction":[{"TID":"O09","Date":"3/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Steam Gift Card","amount":25}], "Total" : "84.99"}); 
db.transaction.insert({"EmpId":"002","transaction":[{"TID":"O10","Date":"5/27/2017","product":[{"product_name":"Playstation Headset","quantity":3,"amount":29.99}]},{"product_name":"GTA 4","amount": 39.99},{"product_name":"Unchartered 2","amount": 49.99}], "Total" : "119.97"}); 
db.transaction.insert({"EmpId":"004","transaction":[{"TID":"O11","Date":"5/27/2017","product":[{"product_name":"Harry Potter","quantity":2,"amount":12.99}]},{"product_name":"Lord Of The Ring's","amount": 9.99}], "Total" : "35.97"}); 

这里是我的查询：

db.transaction.aggregate([{ $match: {EmpId: "001"}}, { $group: {_id: "EmpId", total: {$sum: "Total"}}}]) 

下面是结果：

{ "_id" : "EmpId", "total" : 0 } 

Answer 1

首先请 “总” 值的数字，而不是字符串，否则总和不起作用。

db.transaction.insert({"EmpId":"005","transaction":[{"TID":"O02","Date":"3/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Steam Gift Card","amount":25}], "Total" : 84.99}); 
db.transaction.insert({"EmpId":"001","transaction":[{"TID":"O03","Date":"3/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Playstation Controller","amount":25}], "Total" : 84.99}); 
db.transaction.insert({"EmpId":"003","transaction":[{"TID":"O04","Date":"3/27/2017","product":[{"product_name":"Unchartered 2","quantity":1,"amount":49.99}]}], "Total" : 49.99}); 
db.transaction.insert({"EmpId":"003","transaction":[{"TID":"O05","Date":"3/27/2017","product":[{"product_name":"Playstation 4","quantity":1,"amount":359.99}]},{"product_name":"Battlefield 2","amount":49.99}], "Total" : 409.98}); 
db.transaction.insert({"EmpId":"004","transaction":[{"TID":"O06","Date":"4/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Steam Gift Card","amount":50}], "Total" : 109.99}); 
db.transaction.insert({"EmpId":"001","transaction":[{"TID":"O07","Date":"4/27/2017","product":[{"product_name":"CSGO","quantity":1,"amount":13.99}]},{"product_name":"GTA4","amount": 39.99}], "Total" : 53.98}); 
db.transaction.insert({"EmpId":"002","transaction":[{"TID":"O08","Date":"5/27/2017","product":[{"product_name":"Sparta","quantity":3,"amount":17.99}]},{"product_name":"Action Figures","amount": 9.99}], "Total" : 63.96}); 
db.transaction.insert({"EmpId":"005","transaction":[{"TID":"O09","Date":"3/27/2017","product":[{"product_name":"COD","quantity":1,"amount":59.99}]},{"product_name":"Steam Gift Card","amount":25}], "Total" : 84.99}); 
db.transaction.insert({"EmpId":"002","transaction":[{"TID":"O10","Date":"5/27/2017","product":[{"product_name":"Playstation Headset","quantity":3,"amount":29.99}]},{"product_name":"GTA 4","amount": 39.99},{"product_name":"Unchartered 2","amount": 49.99}], "Total" : 119.97}); 
db.transaction.insert({"EmpId":"004","transaction":[{"TID":"O11","Date":"5/27/2017","product":[{"product_name":"Harry Potter","quantity":2,"amount":12.99}]},{"product_name":"Lord Of The Ring's","amount": 9.99}], "Total" : 35.97}); 

使用“$”字段名称，而不是组查询

db.transaction.aggregate([{ $match: {"EmpId": "001"}}, { $group: {_id: "$EmpId", total: {$sum: "$Total"}}}]) 

这里之前符号结果：

{ 
    "_id" : "001", 
    "total" : 138.97 
}