Which of the following is(are) true about providing security to database servers
? Select all that apply.
-
A、Do
not host a database server on the same server as your web server
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B、Do
not host a database server on a server based system
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C、Do
not use blank password for SA account
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D、Employ
a centralized administration model
題目分析:此題爲數據庫安全題目
A table
CANNOT have one or more of the following index configurations.
-
A、No indexes
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B、A clustered index
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C、clustered index and many non-clustered indexes
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D、Many clustered index
題目分析:聚集索引。索引是通過二叉樹的數據結構來描述的,我們可以這麼理解聚簇索引:索引的葉節點就是數據節點。而非聚簇索引的葉節點仍然是索引節點,只不過有一個指針指向對應的數據塊,故聚集索引規定數據在表中的物理存儲順序,因此一個表只能包含一個聚集索引。但該索引可以包含多個列(組合索引),就像電話簿按姓氏和名字進行組織一樣。
而非聚集索引一個表可以存在多個。
聚集索引存儲記錄是物理上連續存在,而非聚集索引是邏輯上的連續,物理存儲並不連續。
題目分析:黑客
To speed
up data access , we build cache system. In one system , The L1 cache access time is 5 ns , the L2 cache access time is 50 ns and the
memory access time is 400 ns. The L1 cache miss rate is 50% , the L2 cache miss rate is 10%.
The average data access time of this system is:
題目分析:
In which
case(s) would you use an outer join?
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A、The table being joined have NOT NULL columns.
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B、The table being joined have only matched data.
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C、The columns being joined have NULL values.
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D、The table being joined have only unmatched data.
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E、The table being joined have both matched and unmatched data.
題目分析:外連接(數據庫)。outer
join則會返回每個滿足第一個(頂端)輸入與第二個(底端)輸入的聯接的行。它還返回任何在第二個輸入中沒有匹配行的第一個輸入中的行。外連接分爲三種:左外連接,右外連接,全外連接。
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-
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A、code segment
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B、static variable
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C、global variable
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D、external difinitions and references for linking
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E、BSS segment
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-
-
-
A、Line 1
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B、Line 2
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C、Line 3
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D、Line 4
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E、Line 5
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A、Threads share the same address space of the parent process;Processes share the same address space of the parent process. -
B、Changes to the main thread(cancellation,priority change,etc.) may affect the behavior of the other threads of the
process; Changes to the parent process does not affect child processes.
-
C、Multiple threads mar cause deadlock,while multiple processes won't cause deadlock.
-
D、Threads can directly communicate with other threads of its process; Processes must use inter-process communication
to communicate with sibling processes.
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E、None of the above.
-
題目解析:進程是程序的一次執行。線程可以理解爲進程中的執行的一段程序片段。兩者間的差別: 進程間是獨立的,這表現在內存空間,上下文環境;線程運行在進程空間內。 一般來講(不使用特殊技術)進程是無法突破進程邊界存取其他進程內的存儲空間;而線程由於處於進程空間內,所以同一進程所產生的線程共享同一內存空間。
同一進程中的兩段代碼不能夠同時執行,除非引入線程。 線程是屬於進程的,當進程退出時該進程所產生的線程都會被強制退出並清除。 線程佔用的資源要少於進程所佔用的資源。 進程和線程都可以有優先級。 在線程系統中進程也是一個線程。可以將進程理解爲一個程序的第一個線程。
-
-
-
A、Improve memory access pattern to decrease cache misses.
-
B、Use special instructions(e.g. vector instructions) to replace compiler generated assembly code.
-
C、Change an algorithm from recursive implementation to iterative implementation.
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D、Loop unwinding.
-
-
-
A、void* f(int);
-
B、int (*f)();
-
C、void (*f(int , void(*)(int)))(int);
-
D、void (*(*f)(int))();
-
-
-
A、O(lgn)
-
B、O(n)
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C、O(nlgn)
-
D、O(n*n)
-
-
As shown in the graph , start from node B , traverse the nodes on a Depth-First Search(DFS) algorithm , which is(are) the possible traversa sequence(s)?
Select all that apply.
-
-
A、BADECF
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B、BADEFC
-
C、BCAFDE
-
D、BCFDEA
-
E、BFDECA
-
-
-
Let's assume one type of cancer may be mis-diagnosed in the examination. 5 out of 100 people with this cancer will be diagnosed as not having it , and 1 out of 100
people without this cancer will be diagnosed as having it. We know the chance of getting this cancer is around 0.1%. One person was examined and diagnosed of having this cancer, which
of the following value if the closest to the chance of is really having it?
-
-
-
Asume you have an object to describe customer data:
{
ID(7 digit numeric)
Family Name(string)
Account Balance(currency)
}
If you have 500,000 Chinese customers records represented by instances of this object type , what set of data structures is best to get fast retrieval of customers (1) get IDs from Name and
(2) get Name from ID?
-
-
A、(1) Tree with Hash(100 bucket) at leaves(2) Tree with linked list at leaves.
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B、(1) Tree with linked list at leaves(2) Array.
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C、(1) Tree with linked list at leaves(2) Hash(10,000 buckets)
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D、(1) Sort linked list(2) Array.
-
-
-
A、14
-
B、18
-
C、20
-
D、24
-
E、None of the above.
-
-
-
A、1,2,3,4,5
-
B、3,5,1,4,2
-
C、1,2,5,4,3
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D、5,4,3,2,1
-
-
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A、TCP provides a way for applications to send encapsulated IP datagrams and send them without having to establish a connection.
-
B、TCP supports multicasting.
-
C、Port numbers below 1024 are called well-known ports and are reserved for standard services. For example,port 21
is reserved for FTP protocol, and port 25 is for SMTP protocol.
-
D、TCP handles package loss reliably.
-
E、None of the above.