2
我使用mongodb聚合获取不同字段的计数。下面是从mobile
收集一些文件: -Mongodb在单个聚合中使用多个组运算符
{
"title": "Moto G",
"manufacturer": "Motorola",
"releasing": ISODate("2011-03-00T10:26:48.424Z"),
"rating": "high"
}
{
"title": "Asus Zenfone 2",
"manufacturer": "Asus",
"releasing": ISODate("2014-10-00T10:26:48.424Z"),
"rating": "high"
}
{
"title": "Moto Z",
"manufacturer": "Motorola",
"releasing": ISODate("2016-10-12T10:26:48.424Z"),
"rating": "none"
}
{
"title": "Asus Zenfone 3",
"manufacturer": "Asus",
"releasing": ISODate("2016-08-00T10:26:48.424Z"),
"rating": "medium"
}
我能找到manufacturer
和rating
计数,但这个失败:
db.mobile.aggregate([
{
$group: { _id: "$manufacturer", count: { $sum: 1 } }
}, {
$group: { _id: "$rating", count: { $sum: 1 } }
}
])
输出: -
{
"_id" : null,
"count" : 2.0
}
预期输出是这样的: -
{
"_id":"Motorola",
"count" : 2.0
}
{
"_id":"Asus",
"count" : 2.0
}
{
"_id":"high",
"count" : 2.0
}
{
"_id":"none",
"count" : 1.0
}
{
"_id":"medium",
"count" : 1.0
}
谢谢...你才是天才在MongoDB中@chridam – vineet