The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 3: Accessing FILESTREAM Data from Client ApplicationsNon-.NET programming languages like C++ can use the Win32 Open Database Connectivity(ODBC) APIs to create a connection to the desired database and begin a databasetransaction. Listing 3-2 shows an example.//Connect to SQL Server through ODBC using DSN "NorthPole"SQLConnect(hdbc, TEXT("NorthPole"), SQL_NTS, NULL, 0, NULL, 0);//Start a transaction by setting AUTO_COMMIT attribute to OFFSQLSetConnectAttr(hdbc, SQL_ATTR_AUTOCOMMIT, (SQLPOINTER)SQL_AUTOCOMMIT_OFF,SQL_IS_UINTEGER);Listing 3-2:Using C++ to start a transaction on an ODBC connection.When the AUTO_COMMIT attribute is turned OFF on an ODBC connection, the nextT-SQL statement starts an explicit transaction. The transaction stays active until SQL_COMMIT or SQL_ROLLBACK is called explicitly using SQLEndTran().Step 2: Retrieving the logical path name andtransaction contextBefore accessing a FILESTREAM data value, we must retrieve, from SQL Server, thelogical path to the disk file associated with the FILESTREAM data, and the transactioncontext that represents the current database transaction, and then include these values inthe data access request.FILESTREAM data values and cellsIn this chapter, the terms FILESTREAM cell and FILESTREAM data value refer, respectively, to a specificcell in a FILESTREAM table (i.e. the intersection of a given row and column) and the BLOB data storedin a FILESTREAM cell.92