我想把我想用Node JS上的猫鼬制作的查询包起来。这是我的数据集:
{"_id":{"$oid":"5e49c389e3c23a1da881c1c9"},"name":"New York","good_incidents":{"$numberInt":"50"},"salary":{"$numberInt":"50000"},"bad_incidents":"30"}
{"_id":{"$oid":"5e49c3bbe3c23a1da881c1ca"},"name":"Cairo","bad_incidents":{"$numberInt":"59"},"salary":{"$numberInt":"15000"}}
{"_id":{"$oid":"5e49c42de3c23a1da881c1cb"},"name":"Berlin","incidents":{"$numberInt":"30"},"bad_incidents":"15","salary":{"$numberInt":"55000"}}
{"_id":{"$oid":"5e49c58ee3c23a1da881c1cc"},"name":"New York","good_incidents":{"$numberInt":"15"},"salary":{"$numberInt":"56500"}}
我想做的就是获取这些值:
由于每个字段只需要一个值,因此我想尽我所能在一个查询中做到这一点。如果有人带领我走上正确的道路,我会感到很高兴。不需要完整的解决方案
致谢!
答案 0 :(得分:0)
您可以使用MongoDB aggregation运算符执行$facet,该运算符可以一次计算多个聚合。
db.collection.aggregate([
{
$facet: {
repeated_city: [
{
$group: {
_id: "$name",
name: {
$first: "$name"
},
count: {
$sum: 1
}
}
},
{
$match: {
count: {
$gt: 1
}
}
},
{
$sort: {
count: -1
}
},
{
$limit: 1
}
],
bad_incidents: [
{
$group: {
_id: null,
avg_bad_incidents: {
$avg: {
$toInt: "$bad_incidents"
}
}
}
}
],
good_incidents: [
{
$group: {
_id: null,
max_good_incidents: {
$max: {
$toInt: "$good_incidents"
}
}
}
}
],
max_salary: [
{
$match: {
bad_incidents: {
$exists: false
}
}
},
{
$group: {
_id: null,
max_salary: {
$max: {
$toInt: "$salary"
}
}
}
}
]
}
},
{
$replaceWith: {
$mergeObjects: [
{
$arrayElemAt: [
"$repeated_city",
0
]
},
{
$arrayElemAt: [
"$bad_incidents",
0
]
},
{
$arrayElemAt: [
"$good_incidents",
0
]
},
{
$arrayElemAt: [
"$max_salary",
0
]
}
]
}
}
])
[
{
"_id": null,
"avg_bad_incidents": 34.666666666666664,
"count": 2,
"max_good_incidents": 50,
"max_salary": 56500,
"name": "New York"
}
]