Shulou(Shulou.com)06/01 Report--

Each collection data in the MongoDB database can continue to save other collection data, for example, some people save family information.

Example: add data

Db.emp.insert ({"name": "Lin A", "sex": "male", "age": 22, "sal": 8000, "loc": "Beijing", "course": ["Chinese", "mathematics", "English", "music", "politics"], "parents": [{"name": "Lin A father", "age": 50, "job": "farmer"}, {"name": "Lin A mother", "age": 49 "job": "worker"}]})

Db.emp.insert ({"name": "Lin B", "sex": "male", "age": 30, "sal": 8000, "loc": "Beijing", "course": ["Chinese", "mathematics"], "parents": [{"name": "Lin B father", "age": 55, "job": "worker"}, {"name": "Lin B mother", "age": 52, "job": "farmer"}]})

Db.emp.insert ({"name": "Lin C", "sex": "male", "age": 35, "sal": 8000, "loc": "Beijing", "course": ["Chinese", "Mathematics", "English"], "parents": [{"name": "Lin C father", "age": 60, "job": "worker"}, {"name": "Lin C mother", "age": 59, "job": "staff"}]})

Db.emp.insert ({"name": "Lin D", "sex": "male", "age": 28, "sal": 8000, "loc": "Beijing", "course": ["Chinese", "Mathematics", "Politics"], "parents": [{"name": "Lin D Father", "age": 58, "job": "Director"}, {"name": "Lin D Mother", "age": 54, "job": "Director"]})

Db.emp.insert ({"name": "Lin E", "sex": "male", "age": 40, "sal": 8000, "loc": "Beijing", "course": ["language", "politics"], "parents": [{"name": "Lin E father", "age": 70, "job": "worker"}, {"name": "Lin E mother", "age": 68, "job": "Secretary"}]})

The content at this time is a nested collection, and the judgment of the data of this collection can only be done through "$elemMatch".

Example: find out the information of the director among the parents.

> db.emp.find ({"$and": [{"age": {"$gte": 30}}, {"parents": {"$elemMatch": {"job": "Director"}}]}) .pretty ()

{

"_ id": ObjectId ("599148bf0184ff511bf02b95")

"name": "Lin E"

"sex": "male"

"age": 40

"sal": 8000

"loc": "Beijing"

"course": [

"Chinese"

"politics"

]

"parents": [

{

"name": "Father Lin E"

"age": 70

"job": "worker

}

{

"name": "Mother Lin E"

"age": 68

"job": "Director"

}

]

}

Since the conditions of this kind of query are troublesome, try not to be so complicated if possible.

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