MongoDB Query Statement Learning Summary

On the left is the MONGODB query statement, and the right is the SQL statement. Compared with the use, very convenient.

Db.users.find () SELECT * from Users

Db.users.find ({"Age": +}) SELECT * from the users where age = 27

Db.users.find ({"username": "Joe", "Age": +}) SELECT * from the users where "username" = "Joe" and age = 27

Db.users.find ({}, {"username": 1, "email": 1}) Select Username, email from users

Db.users.find ({}, {"username": 1, "_id": 0})//no case//Instant column filter is added, _id will also return; you must explicitly block _id return

Db.users.find ({"Age": {"$gte": +, "$lte": ()}) select * from the users where age >=18 and age <=//$lt (<) $l Te (<=) $gt (>) $gte (>=)

Db.users.find ({"username": {"$ne": "Joe"}}) select * from users where username <> "Joe"

Db.users.find ({"Ticket_no": {"$in": [725, 542, 390]}) SELECT * from the users where Ticket_no in (725, 542, 390)

Db.users.find ({"Ticket_no": {"$nin": [725, 542, 390]}) SELECT * from the users where ticket_no not in (725, 542, 390)

Db.users.find ({"$or": [{"Ticket_no": 725}, {"Winner": True}]}) select * Form users where Ticket_no = 725 or winner = TR Ue

Db.users.find ({"Id_num": {"$mod": [5, 1]}}) select * from Users where (id_num mod 5) = 1

Db.users.find ({"$not": {"Age": +}}) select * from the users where not (age = 27)

Db.users.find ({"username": {"$in": [null], "$exists": True}}) select * from the users where username is null//if directly through find ( {"username": null}) For enquiries, then the "no username" record is screened out

Db.users.find ({"Name":/joey?/i})//Regular query, value is an expression that conforms to Pcre

Db.food.find ({fruit: {$all: ["Apple", "Banana"}})//array of queries, field fruit, contains both "Apple" and "banana" records

Db.food.find ({"fruit.2": "Peach"})//array of queries, field fruit, 3rd (starting from 0) element is peach Record

Db.food.find ({' fruit ': {' $size ': 3}})//array of queries, the number of query arrays is 3 records, $size previously cannot be combined with other operators

Db.users.findOne (criteria, {"Comments": {"$slice": 10}})//array of queries, returning only the first 10 of the arrays comments, or {"$slice": -10}, {"$slice": [ 23, 10]}; Return the last 10, and the middle 10, respectively.

Db.people.find ({"Name.first": "Joe", "Name.last": "Schmoe"})//nested query

Db.blog.find ({"Comments": {"$elemMatch": {"author": "Joe", "score": {"$gte": 5}}})//nested query, only if nested elements are arrays are used,

Db.foo.find ({"$where": "this.x + this.y = = 10"})//complex query, $where of course is very convenient, but inefficient. For complex queries, the order of consideration should be regular---MapReduce--$where

Db.foo.find ({"$where": "function () {return this.x + This.y = = Ten;}"})//$where can support JavaScript functions as query criteria

Db.foo.find (). Sort ({"X": 1}). Limit (1). Skip (10); Return to article (10, 11], sorted by "X"; The order of three limit is arbitrary, should try to avoid using Large-number in Skip