except that age = 0 is valid if your database has toddlers. Hell, even -1 makes sense if you're running a query to get the age of someone at a specific time. th

except that age = 0 is valid if your database has toddlers. Hell, even -1 makes sense if you're running a query to get the age of someone at a specific time. this is why you should try to use NULLs whenever possible