How to write and retrieve records from SQL database?

There are plenty of ways you can solve this problem.

1. You can use data explorer and connect to MS SQL Express to get the data. And then dropping the data fields on form will show you the data explorer. And from here you can easily navigate the data. This method however requires minimum code. And this is only good if you wish to make things quicker in implementation.

Take look at the video that explains this: https://www.youtube.com/watch?v=7creesob0Jw

2. In second method you have to write the code on your own. This method too requires connecting to the data. You have to assign buttons or some way to insert, update and delete the data.

Take a look at the video below to learn how to insert the data: https://www.youtube.com/watch?v=UtE3kkQR7_w

Update data: https://www.youtube.com/watch?v=ZCs1vdwwl0o

Delete Data: https://www.youtube.com/watch?v=nse-xeFp0Og

Hope this helps you write the simple code at first. From here onwards you can write the complex code to write for your case.