Contrast MongoDB with MySQL common action statements

1. The implementation of MongoDB for MySQL common SQL statements

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MySQL: 

SELECT * FROM user 

Mongo: 

db.user.find() 

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MySQl: 

SELECT * FROM user WHERE name = 'foobar' 

Mongo: 

db.user.find({ 'name' : 'foobar' }) 

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MySql: 

INSERT INTO user ('name','age') VALUES ('foobar',25) 

Mongo: 

db.user.insert({ 'name' : 'foobar' , 'age' : 25}) 

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 If you want to increase email this 1 column  

MySql: 

ALTER TABLE user ... 

Mongo: 

db.user.insert({ 'name' : 'foobar' , 'age' : 25 , 'email' : 'foo@bar.com' }) 

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MySql: 

DELETE * FROM user 

Mongo: 

db.user.remove({}) 

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MySql: 

DELETE FROM user WHERE age < 30 

Mongo: 

db.user.remove({ 'age' : {$lt : 30}}) 

$gt:> ; $gte:>= ; $lt:< ; $lte:<= ; $ne:!= 

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MySql: 

UPDATE user SET `age` = 36 WHERE `name` = 'foobar' 

Mongo: 

db.user.update({ 'name' : 'foobar'} , {$set : { 'age' : 36}}) 

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MySQL: 

UPDATE user SET `age` = 'age' + 3 WHERE `name` = 'foobar' 

Mongo: 

db.user.update({ 'name' : 'foobar'} , {$inc : {'age' : 3}}) 

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MySQl: 

SELECT COUNT(*) FROM user WHERE `name` = 'foobar' 

Mongo: 

db.user.find({ 'name' : 'foobar'}).count() 

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MySql: 

SELECT * FROM user limit 10,20 

Mongo: 

db.user.find().skip(10).limit(20) 

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MySQl: 

SELECT * FROM user WHERE `age` IN (25,35,45) 

Mongo: 

db.user.find({ 'age' : {$in : [25,35,45]}}) 

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MySql: 

SELECT * FROM user ORDER BY age DESC 

Mongo: 

db.user.find().sort({ 'age' : -1}) 

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MySQL: 

SELECT DISTINCT(name) FROM user WHERE age > 20 

Mongo: 

db.user.distinct( 'name',{'age' : {$lt : 20}}) 

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MySQL: 

SELECT name, sum(marks) FROM  user GROUP BY name 

Mongo: 

db.user.group({ 

key:{'name':true}, 

cond:{'name':'foo'}, 

reduce:function(obj,prev){prev.msum += obj.marks;}, 

initial:{msum : 0} 

}) 

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MySQL: 

SELECT name FROM user WHERE age < 20 

Mongo: 

db.user.find('this.age < 20' , {name : 1})

2. Compare MongoDB database with MySQL operation

The mongodb query statement is on the left and the sql statement is on the right. It's convenient to use in contrast.

db.users.find() select * from users
db.users.find({"age" : 27}) select * from users where age = 27
db.users.find({"username" : "joe", "age" : 27}) select * from 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  //  Even with column filtering, _id It also returns; It must be explicitly blocked _id return 
db.users.find({"age" : {"$gte" : 18, "$lte" : 30}}) select * from users where age >=18 and age <= 30 // $lt(<) $lte(<=) $gt(>) $gte(>=)
db.users.find({"username" : {"$ne" : "joe"}}) select * from users where username <> "joe"
db.users.find({"ticket_no" : {"$in" : [725, 542, 390]}}) select * from users where ticket_no in (725, 542, 390)
db.users.find({"ticket_no" : {"$nin" : [725, 542, 390]}}) select * from users where ticket_no not in (725, 542, 390)
db.users.find({"$or" : [{"ticket_no" : 725}, {"winner" : true}]}) select * form users where ticket_no = 725 or winner = true
db.users.find({"id_num" : {"$mod" : [5, 1]}}) select * from users where (id_num mod 5) = 1
db.users.find({"$not": {"age" : 27}}) select * from users where not (age = 27)
db.users.find({"username" : {"$in" : [null], "$exists" : true}}) select * from users where username is null //  If you go directly through find({"username" : null}) Query, then joint " There is no username" The record of 1 And screen it out 
db.users.find({"name" : /joey?/i}) //  Regular query, value Is in accordance with PCRE The expression of 
db.food.find({fruit : {$all : ["apple", "banana"]}}) //  A query to an array ,  field fruit , both contain "apple", Contain, "banana" The record of 
db.food.find({"fruit.2" : "peach"}) //  A query to an array ,  field fruit In the first 3 a ( from 0 start ) The element is peach The record of 
db.food.find({"fruit" : {"$size" : 3}}) //  A query to an array ,  The number of elements in the query array is 3 The record, $size Cannot be used in combination with other operators 
db.users.findOne(criteria, {"comments" : {"$slice" : 10}}) //  A query to an array returns only an array comments In the first 10 Yeah, it's ok {"$slice" : -10} .  {"$slice" : [23, 10]};  Return to the end 10 Bar and middle 10 article 
db.people.find({"name.first" : "Joe", "name.last" : "Schmoe"})  //  Nested query 
db.blog.find({"comments" : {"$elemMatch" : {"author" : "joe", "score" : {"$gte" : 5}}}}) //  Nested queries, used only if the nested elements are arrays ,
db.foo.find({"$where" : "this.x + this.y == 10"}) //  Complex queries, $where Very convenient, of course, but inefficient. For complex queries, the order to consider should be   regular  -> MapReduce -> $where
db.foo.find({"$where" : "function() { return this.x + this.y == 10; }"}) // $where Can support javascript Function as a query condition 
db.foo.find().sort({"x" : 1}).limit(1).skip(10); //  Returns the first (10, 11] Article, press "x" sorting ; 3 a limit The order is arbitrary and should be avoided as much as possible skip The use of large-number