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Legal Studies在 MongoDB 中獲取特定值的統計資料
要獲取 MongoDB 中特定值的統計資料，請使用 aggregate()。我們使用文件建立一個集合 −
> db.demo210.insertOne(
... {
... details: [
... {
... ClientName: "Robert"
... },
... {
...
... lientName: "John Doe"
... },
... {
...
... ClientName: "Robert"
... },
... {
...
... ClientName: "Robert"
... },
... {
...
... ClientName: "David Miller"
... }
... ]
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3d99ab03d395bdc21346f9")
}使用 find() 方法從集合中顯示所有文件 −
> db.demo210.find();
這將生成以下輸出 −
{ "_id" : ObjectId("5e3d99ab03d395bdc21346f9"), "details" : [ { "ClientName" : "Robert" }, { "ClientName" : "John Doe" }, { "ClientName" : "Robert" }, { "ClientName" : "Robert" }, { "ClientName" : "David Miller" } ] }以下是獲取特定值統計資料的查詢 −
> db.demo210.aggregate([
... { "$match" : { "details.ClientName" : "Robert" } },
... { "$unwind" : "$details" },
... { "$match" : { "details.ClientName" : "Robert" } },
... { "$group" : { "_id" : "$_id", "Size" : { "$sum" : 1 } } },
... { "$match" : { "Size" : { "$gte" : 2 } } }
...]);這將生成以下輸出 −
{ "_id" : ObjectId("5e3d99ab03d395bdc21346f9"), "Size" : 3 }
更新於: 27-Mar-2020
364 次瀏覽
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