MySQL Connector/C++是最新发布的MySQL连接器，由Sun Microsystems开发。MySQL connector为C++提供面向对象的编程接口（API）和连接MySQL Server的数据库驱动器

# mysql -u root -p

Enter password: admin

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 5

Server version: 5.1.24-rc-standard Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> USE test;

Database changed

mysql> DESCRIBE City;

+----------+-------------+------+-----+---------+-------+

| Field    | Type        | Null | Key | Default | Extra |

+----------+-------------+------+-----+---------+-------+

| CityName | varchar(30) | YES  |       | NULL  |       |

+----------+-------------+------+-----+---------+-------+

1 row in set (0.07 sec)

mysql> SHOW CREATE TABLE City\G

*************************** 1. row ***************************

       Table: City

Create Table: CREATE TABLE `City` (

  `CityName` varchar(30) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=ascii

1 row in set (0.00 sec)

mysql> SELECT * FROM City;

+--------------------+

| CityName           |

+--------------------+

| Hyderabad, India   |

| San Francisco, USA |

| Sydney, Australia  |

+--------------------+

3 rows in set (0.17 sec)

下面的C++示例代码简单演示如何使用MySQL Connector/C++连接本机的MySQL服务。实例代码使用Connector/C++提供的类似于JDBC的API连接到MySQL中的test数据库，实行一条查询语句，从City表中获取所有行数据，从结果集中提取数据并显示在标准输出上，使用"Prepared Statements"插入几行数据到City表中。

# cat MySQLConnectorC++Client.cpp

/* Standard C++ headers */

#include <iostream>

#include <sstream>

#include <memory>

#include <string>

#include <stdexcept>

/* MySQL Connector/C++ specific headers */

#include <driver.h>

#include <connection.h>

#include <statement.h>

#include <prepared_statement.h>

#include <resultset.h>

#include <metadata.h>

#include <resultset_metadata.h>

#include <exception.h>

#include <warning.h>

#define DBHOST "tcp://127.0.0.1:3306"

#define USER "root"

#define PASSWORD "admin"

#define DATABASE "test"

#define NUMOFFSET 100

#define COLNAME 200

using namespace std;

using namespace sql;

static void retrieve_data_and_print (ResultSet *rs, int type, int colidx, string colname) {

    /* retrieve the row count in the result set */

    cout << "\nRetrieved " << rs -> rowsCount() << " row(s)." << endl;

    cout << "\nCityName" << endl;

    cout << "--------" << endl;

    /* fetch the data : retrieve all the rows in the result set */

    while (rs->next()) {

        if (type == NUMOFFSET) {

                       cout << rs -> getString(colidx) << endl;

        } else if (type == COLNAME) {

                       cout << rs -> getString(colname) << endl;

        } // if-else

    } // while

    cout << endl;

} // retrieve_data_and_print()

static void retrieve_dbmetadata_and_print (Connection *dbcon) {

    if (dbcon -> isClosed()) {

        throw runtime_error("DatabaseMetaData FAILURE - database connection closed");

    }

    cout << "\nDatabase Metadata" << endl;

    cout << "-----------------" << endl;

    cout << boolalpha;

    /* The following commented statement won't work with Connector/C++ 1.0.5 and later */

    //auto_ptr < DatabaseMetaData > dbcon_meta (dbcon -> getMetaData());

    DatabaseMetaData *dbcon_meta = dbcon -> getMetaData();

    cout << "Database Product Name: " << dbcon_meta -> getDatabaseProductName() << endl;

    cout << "Database Product Version: " << dbcon_meta -> getDatabaseProductVersion() << endl;

    cout << "Database User Name: " << dbcon_meta -> getUserName() << endl << endl;

    cout << "Driver name: " << dbcon_meta -> getDriverName() << endl;

    cout << "Driver version: " << dbcon_meta -> getDriverVersion() << endl << endl;

    cout << "Database in Read-Only Mode?: " << dbcon_meta -> isReadOnly() << endl;

    cout << "Supports Transactions?: " << dbcon_meta -> supportsTransactions() << endl;

    cout << "Supports DML Transactions only?: " << dbcon_meta -> supportsDataManipulationTransactionsOnly() << endl;

    cout << "Supports Batch Updates?: " << dbcon_meta -> supportsBatchUpdates() << endl;

    cout << "Supports Outer Joins?: " << dbcon_meta -> supportsOuterJoins() << endl;

    cout << "Supports Multiple Transactions?: " << dbcon_meta -> supportsMultipleTransactions() << endl;

    cout << "Supports Named Parameters?: " << dbcon_meta -> supportsNamedParameters() << endl;

    cout << "Supports Statement Pooling?: " << dbcon_meta -> supportsStatementPooling() << endl;

    cout << "Supports Stored Procedures?: " << dbcon_meta -> supportsStoredProcedures() << endl;

    cout << "Supports Union?: " << dbcon_meta -> supportsUnion() << endl << endl;

    cout << "Maximum Connections: " << dbcon_meta -> getMaxConnections() << endl;

    cout << "Maximum Columns per Table: " << dbcon_meta -> getMaxColumnsInTable() << endl;

    cout << "Maximum Columns per Index: " << dbcon_meta -> getMaxColumnsInIndex() << endl;

    cout << "Maximum Row Size per Table: " << dbcon_meta -> getMaxRowSize() << " bytes" << endl;

    cout << "\nDatabase schemas: " << endl;

    auto_ptr < ResultSet > rs ( dbcon_meta -> getSchemas());

    cout << "\nTotal number of schemas = " << rs -> rowsCount() << endl;

    cout << endl;

    int row = 1;

    while (rs -> next()) {

        cout << "\t" << row << ". " << rs -> getString("TABLE_SCHEM") << endl;

        ++row;

    } // while

    cout << endl << endl;

} // retrieve_dbmetadata_and_print()

static void retrieve_rsmetadata_and_print (ResultSet *rs) {

    if (rs -> rowsCount() == 0) {

        throw runtime_error("ResultSetMetaData FAILURE - no records in the result set");

    }

    cout << "ResultSet Metadata" << endl;

    cout << "------------------" << endl;

    /* The following commented statement won't work with Connector/C++ 1.0.5 and later */

    //auto_ptr < ResultSetMetaData > res_meta ( rs -> getMetaData() );

    ResultSetMetaData *res_meta = rs -> getMetaData();

    int numcols = res_meta -> getColumnCount();

    cout << "\nNumber of columns in the result set = " << numcols << endl << endl;

    cout.width(20);

    cout << "Column Name/Label";

    cout.width(20);

    cout << "Column Type";

    cout.width(20);

    cout << "Column Size" << endl;

    for (int i = 0; i < numcols; ++i) {

        cout.width(20);

        cout << res_meta -> getColumnLabel (i+1);

        cout.width(20);

        cout << res_meta -> getColumnTypeName (i+1);

        cout.width(20);

        cout << res_meta -> getColumnDisplaySize (i+1) << endl << endl;

    }

    cout << "\nColumn \"" << res_meta -> getColumnLabel(1);

    cout << "\" belongs to the Table: \"" << res_meta -> getTableName(1);

    cout << "\" which belongs to the Schema: \"" << res_meta -> getSchemaName(1) << "\"" << endl << endl;

} // retrieve_rsmetadata_and_print()

int main(int argc, const char *argv[]) {

    Driver *driver;

    Connection *con;

    Statement *stmt;

    ResultSet *res;

    PreparedStatement *prep_stmt;

    Savepoint *savept;

    int updatecount = 0;

    /* initiate url, user, password and database variables */

    string url(argc >= 2 ? argv[1] : DBHOST);

    const string user(argc >= 3 ? argv[2] : USER);

    const string password(argc >= 4 ? argv[3] : PASSWORD);

    const string database(argc >= 5 ? argv[4] : DATABASE);

    try {

        driver = get_driver_instance();

        /* create a database connection using the Driver */

        con = driver -> connect(url, user, password);

        /* alternate syntax using auto_ptr to create the db connection */

        //auto_ptr  con (driver -> connect(url, user, password));

        /* turn off the autocommit */

        con -> setAutoCommit(0);

        cout << "\nDatabase connection\'s autocommit mode = " << con -> getAutoCommit() << endl;

        /* select appropriate database schema */

        con -> setSchema(database);

        /* retrieve and display the database metadata */

        retrieve_dbmetadata_and_print (con);

        /* create a statement object */

        stmt = con -> createStatement();

        cout << "Executing the Query: \"SELECT * FROM City\" .." << endl;

        /* run a query which returns exactly one result set */

        res = stmt -> executeQuery ("SELECT * FROM City");

        cout << "Retrieving the result set .." << endl;

        /* retrieve the data from the result set and display on stdout */

        retrieve_data_and_print (res, NUMOFFSET, 1, string("CityName"));

        /* retrieve and display the result set metadata */

        retrieve_rsmetadata_and_print (res);

        cout << "Demonstrating Prepared Statements .. " << endl << endl;

        /* insert couple of rows of data into City table using Prepared Statements */

        prep_stmt = con -> prepareStatement ("INSERT INTO City (CityName) VALUES (?)");

        cout << "\tInserting \"London, UK\" into the table, City .." << endl;

        prep_stmt -> setString (1, "London, UK");

        updatecount = prep_stmt -> executeUpdate();

        cout << "\tCreating a save point \"SAVEPT1\" .." << endl;

        savept = con -> setSavepoint ("SAVEPT1");

        cout << "\tInserting \"Paris, France\" into the table, City .." << endl;

        prep_stmt -> setString (1, "Paris, France");

        updatecount = prep_stmt -> executeUpdate();

        cout << "\tRolling back until the last save point \"SAVEPT1\" .." << endl;

        con -> rollback (savept);

        con -> releaseSavepoint (savept);

        cout << "\tCommitting outstanding updates to the database .." << endl;

        con -> commit();

        cout << "\nQuerying the City table again .." << endl;

        /* re-use result set object */

        res = NULL;

        res = stmt -> executeQuery ("SELECT * FROM City");

        /* retrieve the data from the result set and display on stdout */

        retrieve_data_and_print (res, COLNAME, 1, string ("CityName"));

        cout << "Cleaning up the resources .." << endl;

        /* Clean up */

        delete res;

        delete stmt;

        delete prep_stmt;

        con -> close();

        delete con;

    } catch (SQLException &e) {

        cout << "ERROR: SQLException in " << __FILE__;

        cout << " (" << __func__<< ") on line " << __LINE__ << endl;

        cout << "ERROR: " << e.what();

        cout << " (MySQL error code: " << e.getErrorCode();

        cout << ", SQLState: " << e.getSQLState() << ")" << endl;

        if (e.getErrorCode() == 1047) {

            /*

            Error: 1047 SQLSTATE: 08S01 (ER_UNKNOWN_COM_ERROR)

            Message: Unknown command

            */

            cout << "\nYour server does not seem to support Prepared Statements at all. ";

            cout << "Perhaps MYSQL < 4.1?" << endl;

        }

        return EXIT_FAILURE;

    } catch (std::runtime_error &e) {

        cout << "ERROR: runtime_error in " << __FILE__;

        cout << " (" << __func__ << ") on line " << __LINE__ << endl;

        cout << "ERROR: " << e.what() << endl;

        return EXIT_FAILURE;

    }

    return EXIT_SUCCESS;

} // main()

# CC -V

CC: Sun C++ 5.9 SunOS_i386 Patch 124864-09 2008/12/16

# CC -o mysqlconnectorc++client -g0 -xO4 -features=extensions -I/opt/coolstack/mysql_32bit/include/mysql \

     -I/export/expts/MySQLConnectorC++/include/cppconn -L/opt/coolstack/mysql_32bit/lib/mysql \

     -L/export/expts/MySQLConnectorC++/lib -lmysqlclient_r -lmysqlcppconn MySQLConnectorC++Client.cpp

# export LD_LIBRARY_PATH=/opt/coolstack/mysql_32bit/lib/mysql:/export/expts/ConnectorC++/lib/:$LD_LIBRARY_PATH

# ./mysqlconnectorc++client localhost root admin test

Database connection's autocommit mode = 0

Database Metadata

-----------------

Database Product Name: MySQL

Database Product Version: 5.1.24-rc-standard

Database User Name: root@localhost

Driver name: MySQL Connector/C++

Driver version: 1.0.5

Database in Read-Only Mode?: false

Supports Transactions?: true

Supports DML Transactions only?: false

Supports Batch Updates?: true

Supports Outer Joins?: true

Supports Multiple Transactions?: true

Supports Named Parameters?: false

Supports Statement Pooling?: false

Supports Stored Procedures?: true

Supports Union?: true

Maximum Connections: 151

Maximum Columns per Table: 512

Maximum Columns per Index: 16

Maximum Row Size per Table: 2147483639 bytes

Database schemas: 

Total number of schemas = 4

    1. information_schema

    2. ISVe

    3. mysql

    4. test

Executing the Query: "SELECT * FROM City" ..

Retrieving the result set ..

Retrieved 3 row(s).

CityName

--------

Hyderabad, India

San Francisco, USA

Sydney, Australia

ResultSet Metadata

------------------

Number of columns in the result set = 1

   Column Name/Label         Column Type         Column Size

            CityName             VARCHAR                  30

Column "CityName" belongs to the Table: "City" which belongs to the Schema: "test"

Demonstrating Prepared Statements .. 

    Inserting "London, UK" into the table, City ..

    Creating a save point "SAVEPT1" ..

    Inserting "Paris, France" into the table, City ..

    Rolling back until the last save point "SAVEPT1" ..

    Committing outstanding updates to the database ..

Querying the City table again ..

Retrieved 4 row(s).

CityName

--------

Hyderabad, India

San Francisco, USA

Sydney, Australia

London, UK

Cleaning up the resources ..

通过sql::Driver对象实例的sql::Connection成员与MySQL建立连接，sql::Driver对象通过sql::Driver::get_driver_instance函数的返回值设定，而sql::Driver::connect函数返回一个sql::Connection对象。

 

注：

/* driver.h */

Driver* Driver::get_driver_instance()

Connection* Driver::connect(const std::string& URL, const std::string& userName, const std::string& password)

Connection* Driver::connect(std::map<std::string, ConnectPropertyVal> properties)

using namespace sql;

Driver *driver;

Connection *con;

try {

    driver = get_driver_instance();

    con = driver -> connect("tcp://127.0.0.1:3306/test", "root", "admin");

} catch (..) {

    ..

}

..

std::map conn_properties;

ConnectPropertyVal tmp;

tmp.str.val = "unix:///tmp/mysql.sock";

conn_properties [std::string("hostName")] = tmp;

tmp.str.val = "root";

conn_properties [std::string("userName")] = tmp;

tmp.str.val = "admin";

conn_properties [std::string("password")] = tmp;

try {

    driver = get_driver_instance();

    con = driver -> connect(conn_properties);

} catch(..) {

    ..

}

std::auto_ptr < sql::Connection > con ( driver -> connect("tcp://127.0.0.1:3306", "root", "admin") );

				= OR =

use namespace std;

use namespace sql;

auto_ptr < Connection > con ( driver -> connect("tcp://127.0.0.1:3306", "root", "admin") );

当调用Connection::createStatement函数时，返回一个Statement对象，它可以用来向数据库服务器发送SQL语句。一般情况下，Statement对象执行的是不带参数的SQL语句。换句话说，一个Statement对象用于执行静态SQL语句，并返回其执行结果。如果需要执行多次不同输入的SQL语句，可以考虑使用Prepared Statements对象。

/* connection.h */

Statement* Connection::createStatement();

Connection *con;

Statement *stmt;

Statement stmt = con -> createStatement();

/* connection.h */

void Connection::setSchema(const std::string& catalog);

/* statement.h */

ResultSet* Statement::executeQuery (const std::string& sql);

int Statement::executeUpdate (const std::string& sql);

bool Statement::execute (const std::string& sql);

ResultSet* Statement::getResultSet();

uint64_t Statement::getUpdateCount();

Statement *stmt;

ResultSet *res;

res = stmt -> executeQuery ("SELECT * FROM City");

bool retvalue = stmt -> execute ("SELECT * FROM City");

if (retvalue) {

    res = stmt -> getResultSet();

} else {

    ...

}

int updateCount = stmt -> executeUpdate ("INSERT INTO City (CityName) VALUES ('Napier, New Zealand')");

int updateCount = 0;

bool retstatus = stmt -> execute ("INSERT INTO City (CityName) VALUES ('Napier, New Zealand')");

if (!retstatus) {

    updateCount = stmt -> getUpdateCount();

} else {

    ...

}

前面的段落解析到，executeQuery和execute两个函数执行SQL查询语句，前者返回一个ResultSet实例。你可以使用ResultSet对象访问SQL查询语句从数据库返回的数据。没一个ResultSet维护一个游标（指针），它指向其当前数据行。利用游标可以顺序读取数据集中的行。在一行中，列的值可以以任意顺序访问。你可以根据列的位置（offset）或它们的列名/标签来访问，后者具有一定的容错性，尤其是在表的架构发生改变后。使用列标签或列名会使代码更加清晰。另一方面，通过列的索引或位置访问，可以提高性能。

/* resultset.h */

size_t ResultSet::rowsCount() const;

void ResultSet::close();

bool ResultSet::next();

bool ResultSet::previous();

bool ResultSet::last();

bool ResultSet::first();

void ResultSet::afterLast();

void ResultSet::beforeFirst();

bool ResultSet::isAfterLast() const;

bool ResultSet::isBeforeFirst()const;

bool ResultSet::isClosed() const;

bool ResultSet::isNull(uint32_t columnIndex) const;

bool ResultSet::isNull(const std::string& columnLabel) const;

bool ResultSet::wasNull() const;

std::string ResultSet::getString(uint32_t columnIndex) const;

std::string ResultSet::getString(const std::string& columnLabel) const;

int32_t ResultSet::getInt(uint32_t columnIndex) const;

int32_t ResultSet::getInt(const std::string& columnLabel) const;

while (res -> next()) {

    cout << rs -> getString("CityName") << endl;

}

while (res -> next()) {

        cout << rs -> getString(1) << endl;

}

/* Move the cursor to the end of the ResultSet object, just after the last row */

res -> afterLast();

if (!res -> isAfterLast()) {

    throw runtime_error("Error: Cursor position should be at the end of the result set after the last row.");

}

/* fetch the data : retrieve all the rows in the result set */

while (res -> previous()) {

    cout << rs -> getString("CityName") << endl;

}