问答题

为了维护数据库的参照完整性，当删除被参照关系的元组时，系统可能采取哪些做法？（15分）

【参考答案】

为了维护数据库的参照完整性，当删除被参照关系的元组时，系统可能采取如下三种做法（每种做法得5分）： 　　(l) 级联删除......

(↓↓↓ 点击下方‘点击查看答案’看完整答案 ↓↓↓)
<上一题 目录 下一题>
热门 试题

单项选择题
The construct cobegin Statement1; Statement2; coend means Statement1 and Statement2 are to be executed in parallel. The only two atomic actions in this construct are loading thevalue of a variable and storing into a variable.For the program segment x:=0； y:=O； cobegin begin x:=l; y:=y+x; end; begin y:=2; x:=x+3; end coend Which of the following indicate(s) possible values for the variables when the segment finishes execution Ⅰ．x=1,y=2 Ⅱ．x=1,y=3 Ⅲ．x=4,y=6
A． Ⅰ
B． Ⅰ and Ⅱ
C． Ⅰ and Ⅲ
D． Ⅱand Ⅲ
单项选择题
Different quality factors of software can be reflected upon user’s different points of view,through product running,product modification and product transformation. Of the following properties,which one is connected with product running Ⅰ．correctness Ⅱ．robustness Ⅲ．re-use
A． Ⅰonly
B． Ⅱ only
C． Ⅰ+Ⅱ
D． all of above
相关试题