(not studentr.date is null),SQLsql中有这种写法吗？not 字段 is null 这是什么意思？？？？

(not studentr.date is null),SQLsql中有这种写法吗？not 字段 is null 这是什么意思？？？？ I want to date Could not read date from is not a valid date I( )(me)would not recommend that restaurantTom's date of birth is 1st June=Tom( )( )( )1st June. I have date whith spring not on a first date意思? is not a valid date and time 请问: is not a valid date date DATE DATE Cmos system not set 和 date and time not set i talk to sue about our lunch date.i cant meet her today because i am not feeling well.a...i talk to sue about our lunch date.i cant meet her today because i am not feeling well.acan bmust cwould dmight填哪个?为什么? I have a date with spring! I remember date and time,October 怎么和美国女孩拍拖I`m a high school student in Boston,I meet a pretty girl and I want to date herHow do u date the America girl?I don`t know whether she likes me or not,in the Camps,I hug with a lot of girls,but that`s what everybody does.I` 我是用到date（Y-m-d H:i:s）函数的时候,错误提示如下：Warning:date():It is not safe to rely on the system's timezone settings.You are *required* to use the date.timezone setting or the date_default_timezone_set() function.In case you