How can add update install module after modification

[SmartDataSoft]

Hello,

 

We have build a module which is used by some client. After some days there need to add a table for multishop. But they already manipulate the data.

 

So it is not possible to reset the module and recreate the table as in that case old data will lose.

 

I saw many people add there module a update folder.

 

I have tried by no luck.

 

What i want to do is , is there any way if i put my new code and it will show on the module a update button. Once user click to update new database update will work.

 

And there old data remain safe.

 

It will be very helpfull for me if any one can help this.