这是我的数据库。
{
"_id" : ObjectId("579cab6c6aba30f42a57a979"),
"iecode" : "P1111",
"country" : "India",
"totalTreatmentArms" : 3,
"treatmentArms" : [
{
"mechanismOrPkg" : "Mechanism",
"mechanism" : "mechanism1"
},
{
"mechanismOrPkg" : "Mechanism",
"mechanism" : "mechanism2"
},
{
"mechanismOrPkg" : "Package",
"mechanism" : "mechanism1"
}
]
}
{
"_id" : ObjectId("579cab7a6aba30f42a57a97a"),
"iecode" : "P1111",
"country" : "Canada",
"totalTreatmentArms" : 3,
"treatmentArms" : [
{
"mechanismOrPkg" : "Mechanism",
"mechanism" : "mechanism1"
},
{
"mechanismOrPkg" : "Mechanism",
"mechanism" : "mechanism2"
},
{
"mechanismOrPkg" : "Package",
"mechanism" : ""
}
]
}
{
"_id" : ObjectId("579cabac6aba30f42a57a97b"),
"iecode" : "P2222",
"country" : "India",
"totalTreatmentArms" : 1,
"treatmentArms" : [
{
"mechanismOrPkg" : "Package",
"mechanism" : ""
}
]
}
{
"_id" : ObjectId("579cabe76aba30f42a57a97c"),
"iecode" : "P3333",
"country" : "India",
"totalTreatmentArms" : 2,
"treatmentArms" : [
{
"mechanismOrPkg" : "Mechanism",
"mechanism" : "mechanism1"
},
{
"mechanismOrPkg" : "Package",
"mechanism" : ""
}
]
}
请注意，有两个记录，iecode : P1111并且我希望区分结果，iecode因此仅考虑一个记录（任何一个）。
现在我的要求是我要依靠现场mechanismOrPkg。如果它包含值，Package那么我们将加package一。如果值为，Mechanism那么我们将考虑字段的值，并将考虑mechanism其尊重的价值。
所以最终结果将是这样
{
"_id" : null,
"totalPackage" : 3,
"totalMechanism1" : 2,
"totalMechanism2" : 1
}
请询问是否听起来令人困惑。让我知道，即使查询可以进行这种聚合，还是必须进行服务器端过滤？
谢谢。
编辑
mechanismOrPkg的可能值：包或机制
机械装置的可能值：机械装置1或机械装置2
要实现上述要求，就需要$cond在$sum累加器运算符中使用该运算符。该$cond运营商将评估基于其第一个参数（如果）的逻辑条件，然后返回，其中评价是真实的（当时）的第二个参数或第三个参数，其中假（否则）。这会将true/false逻辑转换为$sum分别馈入的1和0数值。因此，例如，当您要汇总“ Package”值的计数时，逻辑如下：
{
"$sum": {
"$cond": [ { "$eq": [ "$treatmentArms.mechanismOrPkg", "Package" ] }, 1, 0 ]
}
}
作为结果管道，您需要运行聚合操作
db.collection.aggregate([
{
"$group": {
"_id": "$iecode",
"treatmentArms": { "$first": "$treatmentArms" }
}
},
{ "$unwind": "$treatmentArms" },
{
"$group": {
"_id": null,
"totalPackage": {
"$sum": {
"$cond": [
{ "$eq": [ "$treatmentArms.mechanismOrPkg", "Package" ] },
1, 0
]
}
},
"totalMechanism1":{
"$sum": {
"$cond": [
{
"$and": [
{ "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
{ "$eq": [ "$treatmentArms.mechanism", "mechanism1" ] }
]
},
1,
0 ]
}
},
"totalMechanism2": {
"$sum": {
"$cond": [
{
"$and": [
{ "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
{ "$eq": [ "$treatmentArms.mechanism", "mechanism2" ] }
]
},
1,
0 ]
}
}
}
}
])
样本输出
{
"_id" : null,
"totalPackage" : 3,
"totalMechanism1" : 2,
"totalMechanism2" : 1
}
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