本文描述了MySQL中的常用SQL语句在MongoDB中的写法，如果你长期使用MySQL而对MongoDB跃跃欲试，这篇简单的文章可以帮助你更快的进入角色。
查询：MySQL:SELECT * FROM userMongo: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里添加一个字段，你必须：ALTER TABLE user….但在MongoDB里你只需要：db.user.insert({‘name’ : ’starlee’, ‘age’ : 25, ‘email’ : ’starlee@starlee.com’})删除：MySQL:DELETE * FROM userMongo:db.user.remove({})MySQL:DELETE FROM user WHERE age < 30Mongo: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’}, {$inc : {‘age’ : 3}})MySQL:SELECT COUNT(*) FROM user WHERE `name` = ’starlee’Mongo:db.user.find({‘name’ : ’starlee’}).count()MySQL:SELECT * FROM user limit 10,20Mongo:db.user.find().skip(10).limit(20)MySQL:SELECT * FROM user WHERE `age` IN (25, 35,45)Mongo:db.user.find({‘age’ : {$in : [25, 35, 45]}})MySQL:SELECT * FROM user ORDER BY age DESCMongo:db.user.find().sort({‘age’ : -1})MySQL:SELECT DISTINCT(name) FROM user WHERE age > 20Mongo:db.user.distinct(‘name’, {‘age’: {$lt : 20}})MySQL:SELECT name, sum(marks) FROM user where name='foo' GROUP BY nameMongo: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 < 20Mongo:db.user.find(‘this.age < 20′, {name : 1})发现很多人在搜MongoDB循环插入数据，下面把MongoDB循环插入数据的方法添加在下面：for(var i=0;i<100;i++)db.test.insert({uid:i,uname:’nosqlfan’+i});上面一次性插入一百条数据，大概结构如下：{ “_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″ }