Mongodb和mongoose聚合查询

  • 分类:【MongoDd
  • 浏览【670】
  • 评论【0】
  • 更新【2016-11-02 17:32:39】

mongdb查询某一字段sum值

需求说明:articles有一个字段pv记录了该文章的访问量,现在要统计所有文章访问量,类似于sql中的sum统计

mongodb中查询

select sum(pv) from articles;
db.articles.aggregate([{$group:{_id:null,pv:{$sum:"$pv"}}}]);
结果:{ "_id" : null, "pv" : 2 }

select sum(pv) from articles where createDate <= '2016-10-20';
db.articles.aggregate([{$match:{createDate:{$lte:"2016-10-20"}}},{$group:{_id:null,pv:{$sum:"$pv"}}}]);
结果:{ "_id" : null, "pv" : 9 }

select sum(pv) from articles where category = 'Nodejs';
db.articles.aggregate([{$match:{category:"Nodejs"}},{$group:{_id:null,pv:{$sum:"$pv"}}}]);
结果:{ "_id" : null, "pv" : 7 }

需要注意$match$group的顺序,反了是不行的,因为这是Aggregation Pipeline(管道流)

mongoose实现方式,与上面sql的顺序对应:

Article.aggregate({ $group: { _id: null, pvCount: { $sum: '$pv' }}}, function(err, doc) {
    console.log("1", doc);
});
Article.aggregate([{$match:{createDate:{$lte:"2016-10-20"}}},{$group:{_id:null, pvCount:{$sum:"$pv"}}}], function(err, doc) {
    console.log("2", doc);
});
Article.aggregate([{$match:{category:"Nodejs"}},{$group:{_id:null, pvCount:{$sum:"$pv"}}}], function(err, doc) {
    console.log("3", doc);
});
1 [ { _id: null, pv: 25 } ]
2 [ { _id: null, pv: 9 } ]
3 [ { _id: null, pv: 7 } ]

参考文档:

https://docs.mongodb.com/manual/aggregation/

https://docs.mongodb.com/manual/reference/operator/aggregation/#aggregation-expression-operators

关键字词:mongodb,mongoose