SQL to Mongo Shell to C++

SQL to Mongo Shell to C++

MongoDB的查询表示为JSON（BSON）对象。此快速参考图表显示了作为SQL的例子，Mongo shell 语法，Mongo的C + +驱动程序的语法。 MongoDB的（和其他的东西，比如一个索引键模式）中的查询表达式表示为BSON。在C + +中，你可以使用BSONObjBuilder（又名 bson::bob ）建立BSON对象，或BSON（）宏。下面的例子假设已经建立的连接C： using namespace bson; DBClientConnection c; c.connect("somehost"); 几个在C + +驱动方法抛出的mongo::DBException ，所以你会想一些在你的程序水平作为一个try / catch语句。

 

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 optionally: 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(*y) FROM users where AGE > 30	db.users.find({age: {'$gt': 30}}).count()	unsigned long long n = c.count("mydb.users", QUERY("age:"<<GT<<30));
UPDATE users SET a=a+2 WHERE b='q'	db.users.update({b:'q'}, {$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();