此外,有时候在添加主键的时候也有 ```sql constraint pk_sc primary key(studentid,courseid) 为什么需要constraint 关键字? 实际上完全可以只要 primary key(studentid,courseid) 。使用constraint pk_sc就是为 primary key(studentid,courseid)建立一个名字,这样我们就能删除这个约束或者修改这个约束。
check (grade between 0 and 100); 修改表SC,增加一个约束并命名为c1,约束的内容是成绩在0到100之间。 例3的SQL SERVER命名执行结果图 在SQL SERVER中,将例3的命名执行之后,可以看到在表SC下方的约束中出现了新的约束c1。如果不对约束命名,系统会对约束进行自动命名,如键列表中的“PK_SC”是系统命名的主键,...
所以 constraint pk_course primary key (cno,tno)表示 course表上存在一个名字叫“pk_course”的主键约束 ，它的主键列是 cno,tno的组合列 下面那个同理 表示 SC表上存在一个名字叫“pk_sc”的主键约束 ，它的主键列是 sno,cno的组合列 这是primary key的资料：
此库支持iOS5.0以上版本(另外:Nav的title滑动不明显,本人写了2个类似的控件),SloppySwiper-demo :代码方式与storyboard方式。 SCNavigation - UINavigation可以右滑返回,隐藏UINavigationBar。 UINavigationController-YRBackGesture - 支持右滑返回手势,标题栏不动。 GHSidebarNav - 现在比较流行使用侧开(侧滑)菜单设计...
In 1997, completed wharf screen wall Premier Li Peng to write a few words of appreciation: “Yangshuo - China traveling famous county” the carved stone crustification project, completes invests 60,000 Yuan.In 2000, carried on to the harbor basin scours, the front water depth amounted to 1.5...
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci) SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability We walk in the dark places no others will enter We stand on the bridge and no one may pass ...
Since the index of a semi-Fredholm operator is locally constant [Sc02], and since each Pδk,,gpn is Fredholm of index 0, it follows that Pδk,p also has index 0. From prior arguments, we know that when g is smooth and p = 2 the kernel of Pδk,p is the set of conformal ...
In this work, we present a scheduling mechanism for deadline sensitive task or lease. It is very impelling and challenging to allocate on-demand resources within the deadline rather than rejecting the lease. The work studies the insight of existing backfilling algorithm that is used to schedule ...
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