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  • mongodb(基础用法)

    驱动和客户端库

    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

    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"
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  • 原文地址：https://www.cnblogs.com/zzyoucan/p/3593958.html
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