mongodb(基础用法)

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https://mongodb-documentation.readthedocs.org/en/latest/ecosystem/drivers.html#id2

https://mongodb-documentation.readthedocs.org/en/latest/ecosystem/drivers/cpp-to-sql-to-mongo-shell.html

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SQL to mongo Shell to C++

MongoDB queries are expressed as JSON (BSON) objects. This quick reference chart shows examples as SQL, mongo shell syntax, and MongoDB C++ driver syntax.

A query expression in MongoDB (and other things, such as an index key pattern) is represented as BSON. In C++ you can use BSONObjBuilder (aka bson::bob) to build BSON objects, or the BSON() macro. The examples below assume a connection c already established:

using namespace bson;

DBClientConnection c;

c.connect("somehost");

Several of the C++ driver methods throw mongo::DBException, so you will want a try/catch statement as some level in your program. Also be sure to call c.getLastError() after writes to check the error code.

SQL	mongo Shell	C++ Driver
INSERT INTO USERS VALUES( 1, 1)	db.users.insert( { a: 1, b: 1 } )	// GENOID is optional. if not done by client, // server will add an _id c.insert("mydb.users", BSON(GENOID<<"a"<<1<<"b"<<1)); // then: string err = c.getLastError();
SELECT a,b FROM users	db.users.find( {}, {a: 1, b: 1 } )	auto_ptr<DBClientCursor> cursor = c.query("mydb.users", Query(), 0, 0, BSON("a"<<1<<"b"<<1));
SELECT * FROM users	db.users.find()	auto_ptr<DBClientCursor> cursor = c.query("mydb.users", Query());
SELECT * FROM users WHERE age=33	db.users.find( { age: 33 } )	auto_ptr<DBClientCursor> cursor = c.query("mydb.users", QUERY("age"<<33)) // or: auto_ptr<DBClientCursor> cursor = c.query("mydb.users", BSON("age"<<33))
SELECT * FROM users WHERE age=33 ORDER BY name	db.users.find( { age: 33 } ).sort( { name: 1 } )	auto_ptr<DBClientCursor> cursor = c.query("mydb.users", QUERY("age"<<33).sort("name"));
SELECT * FROM users WHERE age>33 AND age<=40	db.users.find( { 'age': { $gt:33, $lte:40 } } )	auto_ptr<DBClientCursor> cursor = c.query("mydb.users", QUERY("age"<<GT<<33<<LTE<<40));
CREATE INDEX myindexname ON users(name)	db.users.ensureIndex( {name: 1 } )	c.ensureIndex("mydb.users", BSON("name"<<1));
SELECT * FROM users LIMIT 10 SKIP 20	db.users.find().limit(10).skip(20)	auto_ptr<DBClientCursor> cursor = c.query("mydb.users", Query(), 10, 20);
SELECT * FROM users LIMIT 1	db.users.findOne()	bo obj = c.findOne("mydb.users", Query());
SELECT DISTINCT last_name FROM users WHERE x=1	db.users.distinct( 'last_name', {x: 1} )	// no helper for distinct yet in c++ driver, // so send command manually bo cmdResult; bool ok = c.runCommand( "mydb", BSON("distinct" << "users" << "key" << "last_name" << "query" << BSON("x"<<1)), cmdResult); list<bo> results; cmdResult["values"].Obj().Vals(results);
SELECT COUNT(*) FROM users where AGE > 30	db.users.find( { age: { $gt: 30 } } ).count()	unsigned long long n = c.count("mydb.users", BSON("age"<<GT<<30));
UPDATE users SET a=a+2 WHERE b='q'	db.users.update( { b: 'q' }, { $inc: { a:2 } }, false, true)	c.update("mydb.users", QUERY("b"<<"q"), BSON("$inc"<<BSON("a"<<2)), false, true); // then optionally: string err = c.getLastError(); bool ok = err.empty();
DELETE FROM users WHERE z="abc"	db.users.remove( { z: 'abc' } )	c.remove("mydb.users", QUERY("z"<<"abc")); // then optionally: string err = c.getLastError();

也可以参考

• Several more examples (in shell syntax) are on the SQL to Mongo Mapping Chart page.
• C++ Language Center
• <   Getting Started with the C++ Driver

SQL to MongoDB Mapping Chart

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.

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 _idfield.
aggregation (e.g. group by)	aggregation pipeline See the SQL to Aggregation Mapping Chart.

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

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() anddb.createCollection()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(     { },     { $set: { join_date: new Date() } },     { multi: true } )	See the Data Modeling Concepts, update(), and$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(     { },     { $unset: { join_date: "" } },     { multi: true } )	See Data Modeling Concepts, update(), and$unset for 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() andindexes 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() andindexes 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 $andfor 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, $lte: 50 } } )	Seefind(),$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()andcount() for more information.
SELECT COUNT(user_id) FROM users	db.users.count( { user_id: { $exists: true } } ) or db.users.find( { user_id: { $exists: true } } ).count()	Seefind(),count(), and$exists for more information.
SELECT COUNT(*) FROM users WHERE age > 30	db.users.count( { age: { $gt: 30 } } ) or db.users.find( { age: { $gt: 30 } } ).count()	Seefind(),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)	Seefind(),findOne(), andlimit() for more information.
SELECT * FROM users LIMIT 5 SKIP 10	db.users.find().limit(5).skip(10)	Seefind(),limit(), and skip()for more information.
EXPLAIN SELECT * FROM users WHERE status = "A"