MongoDB Learning Notes (iii)

Query for MONGODB data:

Find Method:

function (Query, field, limit, skip, batchsize, options) {/*query    : Query condition    fields: Returns the column    limit:    Skip:    batchsize:    options: */}

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Querying all data in a collection

Db.user.find (); // When you do not specify a query condition, the default is {} empty document

Specify the fields that need to be returned: By default the _id field is returned, and if you do not want to render the _id field, you can set _id:0 to not return

var key={    "age": 1,    "name": 1}db.user.find ({},key);

Query criteria:

"$lt", "$gt", "$lte", "$gte" operators:

var action={    "age": {"$lte": +, "$GT": +}//20<age<=30} var key={    "_id": 0,// do not return _id, return the age, Name field, other fields do not return    "age" by default : 1,    "name": 1    }db.user.find (action,key);

"$or", "$in" operators:

var action={    "$or":    [        {"$in": [20,25]}},        {"name": {"$ In ": [" Zhang Jie "," Ziyi "]}}    ]}var key=    {" _id ": 0,// do not return _id, return age, Name field, other fields do not return    "age" by default:1    ,"name": 1    }db.user.find (action,key);

"$and" operator:

Cond..

MongoDB Learning Notes (iii)