Function SQLDescribeParam 

pub unsafe extern "system" fn SQLDescribeParam(
    statement_handle: *mut Stmt,
    parameter_number: u16,
    data_type_ptr: *mut SqlDataType,
    parameter_size_ptr: *mut u64,
    decimal_digits_ptr: *mut i16,
    nullable_ptr: *mut i16,
) -> SQLRETURN

Returns the description of a parameter marker associated with a prepared SQL statement. This information is also available in the fields of the IPD.

Returns

SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_STILL_EXECUTING, SQL_ERROR, or SQL_INVALID_HANDLE.