mongodb 和 mysql 的对照

In addition to the charts that follow, you might want to consider the Frequently Asked Questions section for a selection of common questions about MongoDB.

Executables

The following table presents the MySQL/Oracle executables and the corresponding MongoDB executables.

	MySQL/Oracle	MongoDB
Database Server	mysqld/oracle	mongod
Database Client	mysql/sqlplus	mongo

Terminology and Concepts

The following table presents the various SQL terminology and concepts and the corresponding MongoDB terminology and concepts.

SQL Terms/Concepts	MongoDB Terms/Concepts
database	database
table	collection
row	document or BSON document
column	field
index	index
table joins	embedded documents and linking
primary key Specify any unique column or column combination as primary key.	primary key In MongoDB, the primary key is automatically set to the _id field.
aggregation (e.g. group by)	aggregation framework See the SQL to Aggregation Framework Mapping Chart.

Examples

The following table presents the various SQL statements and the corresponding MongoDB statements. The examples in the table assume the following conditions:

• The SQL examples assume a table named users.

• The MongoDB examples assume a collection named users that contain documents of the following prototype:

  {
    _id: ObjectID("509a8fb2f3f4948bd2f983a0"),
    user_id: "abc123",
    age: 55,
    status: 'A'
  }
  

Create and Alter

The following table presents the various SQL statements related to table-level actions and the corresponding MongoDB statements.

SQL Schema Statements	MongoDB Schema Statements	Reference
CREATE TABLE users ( id MEDIUMINT NOT NULL AUTO_INCREMENT, user_id Varchar(30), age Number, status char(1), PRIMARY KEY (id) )	Implicitly created on first insert operation. The primary key_id is automatically added if _id field is not specified. db.users.insert( { user_id: "abc123", age: 55, status: "A" } ) However, you can also explicitly create a collection: db.createCollection("users")	See insert() andcreateCollection()for more information.
ALTER TABLE users ADD join_date DATETIME	Collections do not describe or enforce the structure of its documents; i.e. there is no structural alteration at the collection level. However, at the document level, update() operations can add fields to existing documents using the $set operator. db.users.update( { }, { $set: { join_date: new Date() } }, { multi: true } )	See the Data Modeling Considerations for MongoDB Applications,update(), and $set for more information on changing the structure of documents in a collection.
ALTER TABLE users DROP COLUMN join_date	Collections do not describe or enforce the structure of its documents; i.e. there is no structural alteration at the collection level. However, at the document level, update() operations can remove fields from documents using the $unset operator. db.users.update( { }, { $unset: { join_date: "" } }, { multi: true } )	See Data Modeling Considerations for MongoDB Applications,update(), and $unsetfor more information on changing the structure of documents in a collection.
CREATE INDEX idx_user_id_asc ON users(user_id)	db.users.ensureIndex( { user_id: 1 } )	See ensureIndex()and indexes for more information.
CREATE INDEX idx_user_id_asc_age_desc ON users(user_id, age DESC)	db.users.ensureIndex( { user_id: 1, age: -1 } )	See ensureIndex()and indexes for more information.
DROP TABLE users	db.users.drop()	See drop() for more information.

Insert

The following table presents the various SQL statements related to inserting records into tables and the corresponding MongoDB statements.

SQL INSERT Statements	MongoDB insert() Statements	Reference
INSERT INTO users(user_id, age, status) VALUES ("bcd001", 45, "A")	db.users.insert( { user_id: "bcd001", age: 45, status: "A" } )	See insert() for more information.

Select

The following table presents the various SQL statements related to reading records from tables and the corresponding MongoDB statements.

SQL SELECT Statements	MongoDB find() Statements	Reference
SELECT * FROM users	db.users.find()	See find()for more information.
SELECT id, user_id, status FROM users	db.users.find( { }, { user_id: 1, status: 1 } )	See find()for more information.
SELECT user_id, status FROM users	db.users.find( { }, { user_id: 1, status: 1, _id: 0 } )	See find()for more information.
SELECT * FROM users WHERE status = "A"	db.users.find( { status: "A" } )	See find()for more information.
SELECT user_id, status FROM users WHERE status = "A"	db.users.find( { status: "A" }, { user_id: 1, status: 1, _id: 0 } )	See find()for more information.
SELECT * FROM users WHERE status != "A"	db.users.find( { status: { $ne: "A" } } )	See find()and $ne for more information.
SELECT * FROM users WHERE status = "A" AND age = 50	db.users.find( { status: "A", age: 50 } )	See find()and $and for more information.
SELECT * FROM users WHERE status = "A" OR age = 50	db.users.find( { $or: [ { status: "A" } , { age: 50 } ] } )	See find()and $or for more information.
SELECT * FROM users WHERE age > 25	db.users.find( { age: { $gt: 25 } } )	See find()and $gt for more information.
SELECT * FROM users WHERE age < 25	db.users.find( { age: { $lt: 25 } } )	See find()and $lt for more information.
SELECT * FROM users WHERE age > 25 AND age <= 50	db.users.find( { age: { $gt: 25, $lte: 50 } } )	See find(),$gt, and$lte for more information.
SELECT * FROM users WHERE user_id like "%bc%"	db.users.find( { user_id: /bc/ } )	See find()and $regexfor more information.
SELECT * FROM users WHERE user_id like "bc%"	db.users.find( { user_id: /^bc/ } )	See find()and $regexfor more information.
SELECT * FROM users WHERE status = "A" ORDER BY user_id ASC	db.users.find( { status: "A" } ).sort( { user_id: 1 } )	See find()and sort()for more information.
SELECT * FROM users WHERE status = "A" ORDER BY user_id DESC	db.users.find( { status: "A" } ).sort( { user_id: -1 } )	See find()and sort()for more information.
SELECT COUNT(*) FROM users	db.users.count() or db.users.find().count()	See find()and count()for more information.
SELECT COUNT(user_id) FROM users	db.users.count( { user_id: { $exists: true } } ) or db.users.find( { user_id: { $exists: true } } ).count()	See find(),count(), and $existsfor more information.
SELECT COUNT(*) FROM users WHERE age > 30	db.users.count( { age: { $gt: 30 } } ) or db.users.find( { age: { $gt: 30 } } ).count()	See find(),count(), and $gt for more information.
SELECT DISTINCT(status) FROM users	db.users.distinct( "status" )	See find()anddistinct()for more information.
SELECT * FROM users LIMIT 1	db.users.findOne() or db.users.find().limit(1)	See find(),findOne(), and limit()for more information.
SELECT * FROM users LIMIT 5 SKIP 10	db.users.find().limit(5).skip(10)	See find(),limit(), and skip()for more information.
EXPLAIN SELECT * FROM users WHERE status = "A"	db.users.find( { status: "A" } ).explain()	See find()andexplain()for more information.

Update Records

The following table presents the various SQL statements related to updating existing records in tables and the corresponding MongoDB statements.

SQL Update Statements	MongoDB update() Statements	Reference
UPDATE users SET status = "C" WHERE age > 25	db.users.update( { age: { $gt: 25 } }, { $set: { status: "C" } }, { multi: true } )	See update(), $gt, and $set for more information.
UPDATE users SET age = age + 3 WHERE status = "A"	db.users.update( { status: "A" } , { $inc: { age: 3 } }, { multi: true } )	See update(), $inc, and $set for more information.

Delete Records

The following table presents the various SQL statements related to deleting records from tables and the corresponding MongoDB statements.

SQL Delete Statements	MongoDB remove() Statements	Reference
DELETE FROM users WHERE status = "D"	db.users.remove( { status: "D" } )	See remove() for more information.
DELETE FROM users	db.users.remove( )	See remove() for more information.