It only takes a small programming error — mistaking " Null" for NULL — and suddenly, the computer thinks you don't exist, or at least you can't register an account with your favorite kitty-litter-cleanup-service.
只要一个小小的编程错误,把 " Null " 误认为 " NULL" ,就会突然认为你不存在,或者至少你无法在你最喜欢的猫砂清理服务公司注册账户。