Gets the number of fields in a request.
[in] Request handle received in DatabasePrepare().
Number of fields or -1 in case of an error. To get the error code, use GetLastError(), the possible responses are:
There is no need to call the DatabaseRead() function to get the number of fields of a request created in DatabasePrepare(). For the remaining DatabaseColumnXXX() functions, DatabaseRead() should be preliminarily called.