Question

我有一份文件如下：

{_ ID：1＆＃34; $ FIELD1＆＃34;：10，＆＃34; $ FIELD2＆＃34; 20}

通过mongo db java驱动程序，我们可以使用名为$ total的新字段更新所有文档，该字段将是field1和field2的总和

在Relation数据库中的等价物

更新表格总计=字段1 +字段2

使用mongo DB java驱动程序可以逐个获取记录。

我尝试了以下链接，但它没有给出链接

中指定的结果

https://docs.mongodb.org/manual/reference/operator/aggregation/sum/

db.students.insert({ "_id": 1, "quizzes": [ 10, 6, 7 ], "labs": [ 5, 8 ], "final": 80, "midterm": 75 });
db.students.insert({ "_id": 2, "quizzes": [ 9, 10 ], "labs": [ 8, 8 ], "final": 95, "midterm": 80 });
db.students.insert({ "_id": 3, "quizzes": [ 4, 5, 5 ], "labs": [ 6, 5 ], "final": 78, "midterm": 70 });

查询：

db.students.aggregate([
   {
     $project: {
       quizTotal: { $sum: "$quizzes"},
       labTotal: { $sum: "$labs" },
       examTotal: { $sum: [ "$final", "$midterm" ] }
     }
   }
])

文档中记载的结果：

{ "_id" : 1, "quizTotal" : 23, "labTotal" : 13, "examTotal" : 155 }
{ "_id" : 2, "quizTotal" : 19, "labTotal" : 16, "examTotal" : 175 }
{ "_id" : 3, "quizTotal" : 14, "labTotal" : 11, "examTotal" : 148 }

实际结果：

assert: command failed: {
    "errmsg" : "exception: invalid operator '$sum'",
    "code" : 15999,
    "ok" : 0
} : aggregate failed
Error: command failed: {
    "errmsg" : "exception: invalid operator '$sum'",
    "code" : 15999,
    "ok" : 0
} : aggregate failed
    at Error (<anonymous>)
    at doassert (src/mongo/shell/assert.js:11:14)
    at Function.assert.commandWorked (src/mongo/shell/assert.js:254:5)
    at DBCollection.aggregate (src/mongo/shell/collection.js:1278:12)
    at (shell):1:13
2016-02-06T09:58:49.230+0530 E QUERY    Error: command failed: {
    "errmsg" : "exception: invalid operator '$sum'",
    "code" : 15999,
    "ok" : 0
} : aggregate failed
    at Error (<anonymous>)
    at doassert (src/mongo/shell/assert.js:11:14)
    at Function.assert.commandWorked (src/mongo/shell/assert.js:254:5)
    at DBCollection.aggregate (src/mongo/shell/collection.js:1278:12)
    at (shell):1:13 at src/mongo/shell/assert.js:13
>

$ sum使用Mongo DB aggreagation

0 个答案: