如何使用聚合MongoDB 3.0版获取Mongo数据 [英] How to get Mongo data using aggregate MongoDB version 3.0
问题描述
假设我们有10个集合,那么我们必须基于tag_id查找计数.例如,如果tag_id包含0和1,则我们必须对所有数据进行计数,并对不具有tag_id或tag_id为null的数据进行计数.然后,如果它有未读:false,则输出,计算所有未读.
Suppose we have 10 collections, then we have to find the count on the basis of tag_id. For example, if tag_id contains 0 and 1, then we have to count all the data, as well as counting the data that don't have tag_id, or where tag_id is null. Then if it has unread : false then the output comes, count of all the unread.
查找为false时的tag_id计数和未读计数.
Find the counts of tag_id and counts of unread when false.
{
"_id": ObjectId("5912c7240520df77f0c2c18a"),
"email_id": "54",
"unread": "false",
"__v": NumberLong(0),
"tag_id": ["0"
]
}, {
"_id": ObjectId("5912c71e0520df77f0c2c189"),
"email_id": "55",
"unread": "false",
"__v": NumberLong(0),
"tag_id": [
"1"
]
}, {
"_id": ObjectId("5912c71d0520df77f0c2c186"),
"email_id": "51",
"unread": "false",
"__v": NumberLong(0),
"tag_id": [
"2", "1"
]
}
预期结果:
{
"data": [{
"tag_id": "1",
"count_email": 1,(count of email on the basis of tag_id)
"unread": 9(count the unread on the basis of output of tag_id)
}, {
"tag_id": "3",
"count_email": 45,
"unread": 3
}, {
"tag_id": "2",
"count_email": 5,
"unread": 4
}, {
"id": null,
"count_email": 52,
"unread": 35
}]
}
推荐答案
尝试以下代码 请参阅- https://docs.mongodb.com/manual/reference/operator /aggregation/eq/
Try the following code Refer - https://docs.mongodb.com/manual/reference/operator/aggregation/eq/
https://docs.mongodb.com/manual/reference/运算符/聚合/cond/
https://docs.mongodb.com/manual/reference/运算符/聚合/组/
DB.aggregate([
{$project:
{
tag_id: '$tag_id',
unreadcount: { $cond: [ { $eq: [ '$unread', 'true' ] }, 1, 0 ] }
}},
{ $group: {
_id: '$tag_id',
unread: { $sum: '$unreadcount'},
}}
], function (err, results) {
console.log(results);
})
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