的的Fileds我有一个集合像下面MongoDB的。需要计算一个数组
{ _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:有些文件亘古不变的有名场。
我想查找名称字段的计数。 请建议查询在mongo中查找计数
嗨菲利普感谢您的帮助。我尝试根据您的建议我的查询。 db.transactions.aggregate([{ $ 放松: “body.payload.iemRecords” },{ $ 组:{ _id: “$ body.payload.iemRecords.CID”, 计数:{$总和:1} } } ])但是得到像“”异常:字段路径引用的错误必须以'$'('body.payload.iemRecords',' – Aman 2014-10-06 13:38:08
@Aman,作为前缀看看Deepak的答案。 – bigtunacan 2014-10-06 14:02:31
@Aman您在$ unwind中错过了$ -sign,尝试'$ unwind:“$ body.payload.iemRecords”' – Philipp 2014-10-06 14:21:52