MySQL Backend Reference
SOCI backend for accessing MySQL database.
The SOCI MySQL backend should in principle work with every version of MySQL 5.x. Some of the features (transactions, stored functions) are not available when MySQL server doesn't support them.
|8.0.1||Windows 10||Visual Studio 2017 (15.3.3)|
|5.5.28||OS X 10.8.2||Apple LLVM version 4.2 (clang-425.0.24)|
|5.0.96||Ubuntu 8.04.4 LTS (Hardy Heron)||g++ (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu4)|
Required Client Libraries
The SOCI MySQL backend requires MySQL's
libmysqlclient client library from the MySQL Connector/C.
Note that the SOCI library itself depends also on
libdl, so the minimum set of libraries needed to compile a basic client program is:
-lsoci_core -lsoci_mysql -ldl -lmysqlclient
Connecting to the Database
To establish a connection to a MySQL server, create a
session object using the
mysql backend factory together with a connection string:
session sql(mysql, "db=test user=root password='Ala ma kota'"); // or: session sql("mysql", "db=test user=root password='Ala ma kota'"); // or: session sql("mysql://db=test user=root password='Ala ma kota'");
The set of parameters used in the connection string for MySQL is:
local_infile- should be
MYSQL_OPT_LOCAL_INFILEwill be set.
Once you have created a
session object as shown above, you can use it to access the database, for example:
int count; sql << "select count(*) from invoices", into(count);
SOCI Feature Support
The MySQL backend supports the use of the SOCI
row class, which facilitates retrieval of data which type is not known at compile time.
row::get<T>(), the type you should pass as
T depends upon the underlying database type.
For the MySQL backend, this type mapping is:
|MySQL Data Type||SOCI Data Type||
|FLOAT, DOUBLE, DECIMAL and synonyms||dt_double||double|
|TINYINT, TINYINT UNSIGNED, SMALLINT, SMALLINT UNSIGNED, INT||dt_integer||int|
|INT UNSIGNED||dt_long_long||long long or unsigned|
|BIGINT UNSIGNED||dt_unsigned_long_long||unsigned long long|
|CHAR, VARCHAR, BINARY, VARBINARY, TINYBLOB, MEDIUMBLOB, BLOB,LONGBLOB, TINYTEXT, MEDIUMTEXT, TEXT, LONGTEXT, ENUM||dt_string||std::string|
|TIMESTAMP (works only with MySQL >= 5.0), DATE, TIME, DATETIME||dt_date||std::tm|
(See the dynamic resultset binding documentation for general information
on using the
Binding by Name
int id = 7; sql << "select name from person where id = :id", use(id, "id")
It should be noted that parameter binding of any kind is supported only by means of emulation, since the underlying API used by the backend doesn't provide this feature.
Transactions are also supported by the MySQL backend. Please note, however, that transactions can only be used when the MySQL server supports them (it depends on options used during the compilation of the server; typically, but not always, servers >=4.0 support transactions and earlier versions do not) and only with appropriate table types.
BLOB Data Type
blob interface is not supported by the MySQL backend.
Note that this does not mean you cannot use MySQL's
BLOB types. They can be selected using the usual SQL syntax and read into
std::string on the C++ side, so no special interface is required.
RowID Data Type
rowid functionality is not supported by the MySQL backend.
Nested statements are not supported by the MySQL backend.
MySQL version 5.0 and later supports two kinds of stored routines: stored procedures and stored functions (for details, please consult the procedure MySQL documentation). Stored functions can be executed by using SOCI's procedure class. There is currently no support for stored procedures.
Native API Access
SOCI provides access to underlying datbabase APIs via several
get_backend() functions, as described in the Beyond SOCI documentation.
The MySQL backend provides the following concrete classes for native API access:
|Accessor Function||Concrete Class|
|session_backend * session::get_backend()||mysql_session_backend|
|statement_backend * statement::get_backend()||mysql_statement_backend|