mongo数组查询，如何仅返回当前匹配数组？

Question

db.test.find();{_id:ObjectId('55e99a2190df7a911d6ed1f1'),list:[{"aa":10,"data":"test"},{"aa":1,"data":"test"}]}db.test.find({_id:ObjectId('55e99a2190df7a911d6ed1f1'),list:{'$elemMatch':{'aa':1}}})预期结果：{_id:ObjectId('55e99a2190df7a911d6ed1f1'),list:{"aa":1,"data":"test"}

Answer 1

>db.customer.find().pretty()
{
"_id":ObjectId("559bb1d1d39f0dcac2658f8e"),
"cust_id":"abc123",
"ord_date":ISODate("2012-10-03T16:00:00Z"),
"status":"A",
"price":25,
"items":[
{
"sku":"mmm",
"qty":5,
"price":2.5
},
{
"sku":"nnn",
"qty":5,
"price":2.5
}
]
}
{
"_id":ObjectId("559bb1ead39f0dcac2658f8f"),
"cust_id":"abc123",
"ord_date":ISODate("2012-10-03T16:00:00Z"),
"status":"B",
"price":30,
"items":[
{
"sku":"mmm",
"qty":6,
"price":3.5
},
{
"sku":"nnn",
"qty":6,
"price":3.5
}
]
}
{
"_id":ObjectId("559bb200d39f0dcac2658f90"),
"cust_id":"abc123",
"ord_date":ISODate("2012-10-03T16:00:00Z"),
"status":"C",
"price":35,
"items":[
{
"sku":"mmm",
"qty":7,
"price":4.5
},
{
"sku":"nnn",
"qty":7,
"price":4.5
}
]
}
>db.customer.find({"items.qty":6},{"items.$":1}).pretty()//只返回和查询条件匹配的那一个元素
{
"_id":ObjectId("559bb1ead39f0dcac2658f8f"),
"items":[
{
"sku":"mmm",
"qty":6,
"price":3.5
}
]
}
查询匹配的内嵌文档，你也可以直接查询，如：
>db.customer.find({"items.qty":6}).pretty()
{
"_id":ObjectId("559bb1ead39f0dcac2658f8f"),
"cust_id":"abc123",
"ord_date":ISODate("2012-10-03T16:00:00Z"),
"status":"B",
"price":30,
"items":[
{
"sku":"mmm",
"qty":6,
"price":3.5
},
{
"sku":"nnn",
"qty":6,
"price":3.5
}
]
}
对应你上面的查询实现：
>db.customer.find({"_id":ObjectId("559bb1ead39f0dcac2658f8f"),items:{'$elemMatch':{'sku':"mmm"}}},{"items.$":1}).pretty()
{
"_id":ObjectId("559bb1ead39f0dcac2658f8f"),
"items":[
{
"sku":"mmm",
"qty":6,
"price":3.5
}
]
}
db.test.find({_id:ObjectId('55e99a2190df7a911d6ed1f1'),list:{'$elemMatch':{'aa':1}}},{"list.$":1}).pretty()