我的MongoDB文档如下所示：

{StatCode : "...", LoadTime  : "..."}

+-----+----------+------------+
| _id | StatCode |  LoadTime  |
+-----+----------+------------+
|   1 |      200 |      0,345 |
|   2 |      200 |      0,234 |
|   3 |      200 |      0,396 |
|   4 |      200 |      1,234 |
|   5 |      200 |      2,564 |
|   6 |      200 |      0,437 |
|   7 |      301 |      0,523 |
|   8 |      301 |      0,628 |
|   9 |      301 |      0,712 |
|  10 |      200 |      1,784 | 
+-----+----------+------------+

+----------+-------+
| Info_id  | Count |
+----------+-------+
| Slowest  |     1 |
| Slow     |     2 |
| Medium   |     3 |
| Fast     |     4 |
+----------+-------+

{
    "_id" : 1,
    "LoadTime" : NumberLong(345),
    "StatCode" : 200
}
{
    "_id" : 2,
    "LoadTime" : NumberLong(234),
    "StatCode" : 200
}
....
{
    "_id" : 9,
    "LoadTime" : NumberLong(712),
    "StatCode" : 301
}
{
    "_id" : 10,
    "LoadTime" : NumberLong( 1784),
    "StatCode" : 200
}

最佳答案

您需要的是$cond运算符和许多带有$and的嵌套条件。但这应该给你你想要的。

db.collection.aggregate([
    {"$group": {
      "_id": {"$cond": [
          {"$gte": ["$LoadTime", 2000] },
          "Slowest",                                   // return "Slowest" where true
          {"$cond": [
              {"$and": [
                  {"$lt": ["$LoadTime", 2000] },
                  {"$gte": ["$LoadTime", 1000] }
              ]},
              "Slow",                                  // then "Slow" here where true
              {"$cond": [
                  {"$and": [
                      {"$lt": ["$LoadTime", 1000] },
                      {"$gte": ["$LoadTime", 500 ] }
                  ]},
                  "Medium",                            // then "Medium" where true
                  "Fast"                               // and finally "Fast" < 500
              ]}
          ]}
      ]},
      "count": {"$sum": 1}
    }},
    {"$sort": { "count": 1 }}
])

          {"$cond": [                             // Evaluate here
              {"$and": [                          // Within the range of the next 2
                  {"$lt": ["$LoadTime", 2000] },
                  {"$gte": ["$LoadTime", 1000] }
              ]},
              "Slow",                            // true condition - return
              {"$cond": [                        // false - move to next eval

db.collection.aggregate([
    {"$group": {
      "_id": {"$cond": [
          {"$gte": ["$LoadTime", 2000] },
          "Slowest",
          null
       ]}
    }}
])

db.collection.aggregate([
    {"$group": {
      "_id": {"$cond": [
          {"$and": [
              {"$lt": ["$LoadTime", 2000] },
              {"$gte": ["$LoadTime", 1000] }
          ]},
          "Slow",
          null
      ]}
    }}
])

db.collection.aggregate([
    {"$group": {
      "_id": {"$cond": [
          {"$gte": ["$LoadTime", 2000] },       // Caught everything over 2000
          "Slowest",
          {"$cond": [
              {"$gte": ["$LoadTime", 1000] }    // Catch things still over 1000
              "Slow",
              {"$cond": [                       // Things under 1000 go here

              // and so on

关于mongodb - Mongodb聚合，如何按间隔标准计算文件？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21965585/