VB.NET | SQL Code Cleanup
As you're beginner, your code can be considered ok.

However you may want to consider following points which help you to write reliable (maintainable) code and improve performance.


You want to store connectionstring to some common place like web.config. You don't have to find and change it all over the place you used it, just change at one place and it will be reflected.
You may want to use stored procedure instead of inline query. With stored procedure, your sql code will be more maintainable and you can go through execution plan of sql code to find out any performance bottleneck. To change sql code you don't have to modify and compile your .net code.


I hope it helps!