How to customize bcs columns as drop down from another table values in sharepoint

Question

I am working on sharepoint online. I created Bcs of Employeesalary table. In that employeeID coming as textbox. But i need to change the control as dropdownlist

The datas for dropdown from employee table.

Is it possible using simple modification in infopath or have to do weebpart for that?

Is it possible means by webpart or anything else means, please give me some samples...