CppDB - ODBC bridge - "odbc"

ODBC backend allows to connect to almost any existing SQL database via ODBC driver and provides much more convenient interface that ODBC C API.

Unlike other backends, this one is not loaded dynamically by default but rather linked directly to cppdb library.

Connection String

The driver name is "odbc", but the cppdb::session::engine() returns "unknown" unless "@engine" property is specified.

Connection Properties are passed as is into ODBC connection string, so for example for connecting to some database you may just simply specify:

odbc:DSN=MySource;UID=myuser;PWD=secret

However there are several additional internal properties that define how cppdb treats the ODBC connection:

• @engine - the type of underlying database engine, it allows the backend to customise the behavior and provide support for features missing in ODBC API itself.
  Currently following engine names provide additional values: "mysql", "sqlite3", "postgresql", "mssql". It allows the driver to support cppdb::statement::sequence_last() or cppdb::statement::last_insert_id() functionality.
• @utf - with options "narrow" - the default and "wide". This option specifies how to deal with Unicode. If the "narrow" option is used (default) it would pass strings as is to the backend assuming that is supports UTF-8 natively using so called "ANSI" API , otherwise, it would use so called "Wide" API and convert the strings to UTF-16 and use wide character functions.
  

  Note:

  you should almost always use narrow option as most ODBC drivers support UTF-8 happily, however when you work with MS SQL under windows you would probably want to use wide API for operation on strings.

• @sequence_last - the SQL statement that is used for retrieving the last created id. You need to specify this if you want to use cppdb::statement::sequence_last() or cppdb::statement::last_insert_id() and the engine is not one of mysql sqlite3, postgresql or mssql.
  If the statement contains "?" mark the parameter of cppdb::statement::sequence_last() would be binded to it, otherwise the parameter is ignored.

Implementation Details

Both prepared statements use SQLPrepare API and unprepared statements use SQLExecDirect API. All data is fetched using SQLGetData in order to support variable text length.

Following statements are used for fetching last insert id:

• sqlite3 - "select last_insert_rowid()"
• mysql - "select last_insert_id()"
• postgresql - "select currval(?)"
• mssql - "select @@identity"

If the engine is not one of the above and "@sequence_last" property is not defined the cppdb::not_supported_by_backend exception would be thrown.

cppdb::session::escape() functionality is not supported as actual escaping rules vary by the specific RDBMS and attempt to use them would cause cppdb::not_supported_by_backend exception.