I'm a beginner, I want to take off

I am a newbie, I want to take off the mysql database, c # write programs, c/s structure, createtableuser (idvarchar (10), namevarchar (20) passvarchar (20) isloginvarchar (20) & nbsp; I'm a Cainiao and want to take off
Mysql database, c # written program, c/s structure,

Create table user
(
Id varchar (10 ),
Name varchar (20)
Pass varchar (20)
Islogin varchar (20)
)
Insert into user
Select '01', 'A1' A1'
Insert into user
Select '02 ', 'A2', 'A2 ', '0'
The user content is as follows:
Name pass islogin
A1 a1 1
A2 a2 0

Now I want to write a verification code to verify the user name and password. when the name pass content entered by the a1 user is correct, change islogin to 1 and islogin to 0 by default, indicating that the user has logged on, you cannot log on when you have the same user name. When the user exits, the islogin value is changed to 0.

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Business logic issues do not involve complex SQL statements.
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What's your problem?
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This function should be implemented in your LOGIN code and LOGOUT code. Not implemented in the database.
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If the islogin is detected to be 1 before logon, the system prompts "this account has been logged on. please wait for it to exit ".