的的Fileds我有一個集合像下面MongoDB的。需要計算一個數組
{ _id: 1, zipcode: "63109", students: [
{ name: "john", school: 102, age: 10 },
{ name: "jess", school: 102, age: 11 },
{ name: "jeff", school: 108, age: 15 }
] }
{ _id: 2, zipcode: "63110", students: [
{ name: "ajax", school: 100, age: 7 },
{ name: "achilles", school: 100, age: 8 },
] }
{ _id: 3, zipcode: "63109", students: [
{ school: 100, age: 7 },
{ school: 100, age: 8 },
] }
{ _id: 4, zipcode: "63109", students: [
{ name: "barney", school: 102, age: 7 },
{ name: "ruth", school: 102, age: 16 },
] }
注:有些文件亙古不變的有名場。
我想查找名稱字段的計數。 請建議查詢在mongo中查找計數
嗨菲利普感謝您的幫助。我嘗試根據您的建議我的查詢。 db.transactions.aggregate([{ $ 放鬆: 「body.payload.iemRecords」 },{ $ 組:{ _id: 「$ body.payload.iemRecords.CID」, 計數:{$總和:1} } } ])但是得到像「」異常:字段路徑引用的錯誤必須以'$'('body.payload.iemRecords',' – Aman 2014-10-06 13:38:08
@Aman,作爲前綴看看Deepak的答案。 – bigtunacan 2014-10-06 14:02:31
@Aman您在$ unwind中錯過了$ -sign,嘗試'$ unwind:「$ body.payload.iemRecords」' – Philipp 2014-10-06 14:21:52