Bases de Datos

MySQL term	Mongo term/concept
database	database
table	collection
index	index
row	BSON document
column	BSON field
join	embedding and linking
primary key	_id field
group by	aggregation

SQL Statement	Mongo Statement
CREATE TABLE USERS (a Number, b Number)	implicit; can also be done explicitly with db.createCollection("mycoll")
ALTER TABLE users ADD ...	implicit

INSERT INTO USERS VALUES(3,5)	db.users.insert({a:3,b:5})

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:{$gt:33}})
SELECT * FROM users WHERE age!=33	db.users.find({age:{$ne: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})
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()
SELECT order_id FROM orders o, order_line_items li WHERE li.order_id=o.order_id AND li.sku=12345	db.orders.find({"items.sku":12345},{_id:1})
SELECT customer.name FROM customers,orders WHERE orders.id="q179" AND orders.custid=customer.id	var o = db.orders.findOne({_id:"q179"}); var name = db.customers.findOne({_id:o.custid})

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()

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})

EXPLAIN SELECT * FROM users WHERE z=3	db.users.find({z:3}).explain()

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'});

Sorting (clasificación): consultas ordenadas.
Las consultas en MongoDB pueden devolver los resultados ordenados.
Ejemplo:Para devolver todos los documentos y ordenar por apellido en orden ascendente,la consulta seria de la siguiente manera:

db.registro.find({}).sort({apellido: 1});

slaveOk (consultas secundarias):

Cuando se consulta un conjunto de réplicas, para realizar una consulta (arbitrariamente seleccionado) secundaria, la consulta se puede ejecutar con la opción slaveOk.
En la consola mongo, para indicar el modo slaveOk, escriba lo siguiente:

rs.slaveOk (); / / permiten consultar una secundaria
db.users.find ()

Al indicar slaveOk, estamos declarando que "es una lectura secundaria".