MySQL和MongoDB语句的写法对照

查询：
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 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})

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″ }

简易对照表
SQL Statement                                                  Mongo Query Language Statement
CREATE TABLE USERS (a Number, b Number)         implicit; can be done explicitly
INSERT INTO USERS VALUES(1,1)                             db.users.insert({a:1,b:1})
SELECT a,b FROM users                                           db.users.find({}, {a:1,b:1})
SELECT * FROM users                                              db.users.find()
SELECT * FROM users WHERE age=33                      db.users.find({age:33})
SELECT a,b FROM users WHERE age=33                   db.users.find({age:33}, {a:1,b:1})
SELECT * FROM users WHERE age=33 ORDER BY name                db.users.find({age:33}).sort({name:1})
SELECT * FROM users WHERE age>33                     db.users.find({'age':{$gt:33}})})
SELECT * FROM users WHERE age<33                     db.users.find({'age':{$lt:33}})})
SELECT * FROM users WHERE name LIKE "%Joe%"                                   db.users.find({name:/Joe/})
SELECT * FROM users WHERE name LIKE "Joe%"                               db.users.find({name:/^Joe/})
SELECT * FROM users WHERE age>33 AND age<=40                                   db.users.find({'age':{$gt:33,$lte:40}})})
SELECT * FROM users ORDER BY name DESC                                   db.users.find().sort({name:-1})
CREATE INDEX myindexname ON users(name)                                   db.users.ensureIndex({name:1})
CREATE INDEX myindexname ON users(name,ts DESC)                                   db.users.ensureIndex({name:1,ts:-1})
SELECT * FROM users WHERE a=1 and b='q'                                   db.users.find({a:1,b:'q'})
SELECT * FROM users LIMIT 10 SKIP 20                                   db.users.find().limit(10).skip(20)
SELECT * FROM users WHERE a=1 or b=2                          db.users.find( { $or : [ { a : 1 } , { b : 2 } ] } )
SELECT * FROM users LIMIT 1                                          db.users.findOne()
EXPLAIN SELECT * FROM users WHERE z=3                                   db.users.find({z:3}).explain()
SELECT DISTINCT last_name FROM users                                   db.users.distinct('last_name')
SELECT COUNT(*y) FROM users                                            db.users.count()
SELECT COUNT(*y) FROM users where AGE > 30                             db.users.find({age: {'$gt': 30}}).count()
SELECT COUNT(AGE) from users                                       db.users.find({age: {'$exists': true}}).count()
UPDATE users SET a=1 WHERE b='q'                                   db.users.update({b:'q'}, {$set:{a:1}}, false, true)
UPDATE users SET a=a+2 WHERE b='q'                                   db.users.update({b:'q'}, {$inc:{a:2}}, false, true)
DELETE FROM users WHERE z="abc"                                    db.users.remove({z:'abc'});

FROM:http://yjc2020.iteye.com/blog/1128056