[引用]MongoDB 對應 Mysql 語法

原文: http://blog.nosqlfan.com/html/287.html
MongoDB躍躍欲試，這篇簡單的文章可以幫助你更快的進入角色。

查詢：

MySQL:

SELECT * FROM user

Mongo:

db.user.find()

MySQL:

SELECT * FROM user WHERE name = 'starlee'

Mongo:

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

插入：

MySQL:

INSERT INOT user (`name`, `age`) values ('starlee',25)

Mongo:

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

如果你想在MySQL裡添加一個字段，你必須：
ALTER TABLE user….
但在MongoDB裡你只需要：
db.user.insert({'name' : 'starlee', 'age' : 25, 'email' : 'starlee@starlee.com'})

刪除：

MySQL:

DELETE * FROM user

Mongo:

db.user.remove({})

MySQL:

DELETE FROM user WHERE age < 30

Mongo:

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

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

更新:

MySQL:

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

Mongo:

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

MySQL:

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

Mongo:

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

MySQL:

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

Mongo:

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

MySQL:

SELECT * FROM user limit 10,20

Mongo:

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

MySQL:

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

Mongo:

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

MySQL:

SELECT * FROM user ORDER BY age DESC

Mongo:

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

MySQL:

SELECT DISTINCT(name) FROM user WHERE age > 20

Mongo:

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

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}
});

MySQL:

SELECT name FROM user WHERE age < 20

Mongo:

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

發現很多人在搜MongoDB循環插入數據，下面把MongoDB循環插入數據的方法添加在下面：

for(var i=0;i<100;i++)db.test.insert({uid:i,uname:'nosqlfan'+i});

上面一次性插入一百條數據，大概結構如下：
{ "_id" : ObjectId("4c876e519e86023a30dde6b8〞), "uid" : 55, "uname" : "nosqlfan55〞 }
{ "_id" : ObjectId("4c876e519e86023a30dde6b9〞), "uid" : 56, "uname" : "nosqlfan56〞 }
{ "_id" : ObjectId("4c876e519e86023a30dde6ba"), "uid" : 57, "uname" : "nosqlfan57〞 }
{ "_id" : ObjectId("4c876e519e86023a30dde6bb"), "uid" : 58, "uname" : "nosqlfan58〞 }
{ "_id" : ObjectId("4c876e519e86023a30dde6bc"), "uid" : 59, "uname" : "nosqlfan59〞 }
{ "_id" : ObjectId("4c876e519e86023a30dde6bd"), "uid" : 60, "uname" : "nosqlfan60〞 }