Mongodb组和排序 [英] Mongodb group and sort

问题描述

如何为Mongo转换以下Sql查询?

select a,b,sum(c) csum from coll where active=1 group by a,b order by a

有什么方法可以使用Mongo执行组和排序查询吗?

Is there any way to execute a group and sort query with Mongo?

推荐答案

受此示例在mongo的网站上.

Inspired by this example on mongo's website.

生成虚拟数据:

> db.stack.insert({a:1,b:1,c:1,active:1})
> db.stack.insert({a:1,b:1,c:2,active:0})
> db.stack.insert({a:1,b:2,c:3,active:1})
> db.stack.insert({a:1,b:2,c:2,active:0})
> db.stack.insert({a:2,b:1,c:3,active:1})
> db.stack.insert({a:2,b:1,c:10,active:1})
> db.stack.insert({a:2,b:2,c:10,active:0})
> db.stack.insert({a:2,b:2,c:5,active:1})

MONGO查询:

> db.stack.aggregate(
... {$match:{active:1}},
... {$group:{_id:{a:"$a", b:"$b"}, csum:{$sum:"$c"}}},
... {$sort:{"_id.a":1}})

结果:

{"result" : [
    {"_id" : {"a" : 1,"b" : 2},"csum" : 3},
    {"_id" : {"a" : 1,"b" : 1},"csum" : 1},
    {"_id" : {"a" : 2,"b" : 2},"csum" : 5},
    {"_id" : {"a" : 2,"b" : 1},"csum" : 13}
],"ok" : 1}

(注意:我对shell结果进行了重新格式化，以使其更具可读性)

(NOTE: I reformatted the shell result a bit so it is more readable)

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