Parameter markers act as place holders for values that are supplied by the program when you instruct the data source to run the SQL statement.
When you use SQLPrepare, the statement that contains the parameter markers is passed to the data source to be prepared by the SQL Optimizer. The Optimizer builds a plan of the statement and holds it for later reference. Each parameter marker must be associated with a program variable (strictly, a pointer to a program variable), and SQLBindParameter is used for this purpose.
SQLBindParameter is a complex function. Careful study of the relevant section in the Microsoft® ODBC Software Development Kit and Programmer's Reference ISBN 1-57231-516-4 is strongly recommended. For most SQL statements, using SQLBindParameter provides input information to the function, but with stored procedures it also can receive data back.
After you have prepared the statement and bound the parameters, use SQLExecute to set to the data source the current values of the associated variables.