I went to a company for an interview in the morning and gave me a question. After 20 minutes, I answered a few questions, but I didn't have enough self-motivation. I don't have many questions. I remember the following:
1 . Two string variables String A, B; program to connect two strings with ASCII Storage
For example: String A = " ABCD " , String B = " Defgh " ; Returned result: abcddefgh
Requirements:
A. You cannot use any class library functions.
B. Write several test cases to test it.
I don't know. ~ .. ~
2 . Talk about processes, threads, and applications.ProgramDomain differences
A process is the execution process of concurrent programs on the dataset.
A thread is a part of a process and the execution flow of one or more commands of the process. It can reduce the system overhead caused by the process and improve the concurrency of the system.
. In. net, the application domain [appdomain] is an independent execution environment of the Program, providing isolation, uninstallation, and security for the execution of managed code.
A process can have multiple AppDomains
Appdomain has no one-to-one relationship with the thread, but at a specific time, a thread must be in an appdomain.
3 . Differences between dataset and datareader
Datareader and dataset are used to retrieve and store data, but they also have some differences.
A DataSet object is a data cache in the memory. It contains a set of relationships between tables and these tables. Each table contains a set of columns. It can be considered as an offline database, supports closed connections.
Datareader provides a fast, forward-only, and read-only data stream from the database. When reading data from datareader, you need to open the connection object and maintain a connection with the database, that is, it does not support closed connections.
4 .Asp.net has several authentication methods. Which one have you used in your recent project? Why?
> Asp.net supports Forms authentication, window authentication, and passport authentication.
> Our project adopts forms Verification
>
Window authentication is based on IIS identity authentication and does not conform to the business model.
Passport authenticaiton is a Microsoft-based authentication server, which is not flexible and difficult to control.
Forms authenctication is based on cookies and is used to save user creden.
Therefore, we use forms verification.
5 . Scores table: ID name score
1 Zhang San 80
2 Zhang San 89
3 Zhang San 89
4 Li Si 89
5 Li Si 89
6 Wang Wu 89
Requirements:
A. Write an SQL statement. Only one record is used for each name.
-- Create Test Database
Create Database interview
Go
Use interview
Go
-- Create a table
Create Table scores (ID Int , Name nvarchar ( 50 ), Score Int )
Go
-- Insert data
Insert scores select 1 , ' Zhang San ' , 80
Union all select 2 , ' Zhang San ' , 89
Union all select 3 , ' Zhang San ' , 89
Union all select 4 , ' Li Si ' , 89
Union all select 5 , ' Li Si ' , 89
Union all select 6 , ' Wang Wu ' , 89
Go
-- View data
Select * From scores
-- A
-- Method1
Select * From scores
Where ID In
(Select max (ID)
From scores
Group by name)
-- Method2
Select * From scores
Where ID In
(
Select top 1 ID from scores B where a. Name = B. Name order by ID DESC
)
-- Method3
Select * From scores
Where
1 > (
Select count ( 0 ) From scores B
Where B. Name = A. Name and B. ID > A. ID
)
-- Method4
Select * From scores
Where
Not exists (
Select * From scores B
Where B. Name = A. Name and B. ID > A. ID
)
B. Write a statement to delete the table record so that each name has only one record
Delete from scores
Where id not In
(
Select a. ID from scores
Where
Not exists (
Select * From scores B
Where B. Name = A. Name and B. ID > A. ID
)
)
Select * From scores
C. Design a data table at the database design level so that a user can have only one record in the table
Create Table students
(
ID Int Identity ( 1 , 1 ) Primary key,
Name nvarchar ( 100 ) Not null
Unique nonclustered)
Go
Insert students
Select a. name from scores
Where
Not exists (
Select * From scores B
Where B. Name = A. Name and B. ID > A. ID
)
Go
Select * From students
