How to add External Content type To customSharePoint list ?

We have a requirement Creating External Content type in sharpoint 2013 based on that SQL database Table.

For example in sql i have four database(db1,db2,db3,db4) and sharepoint i have 4 custom list(list1,list2,list3,list4).

db1 having 4 columns

EMPID  NAME    ADDRESS   PhoneNumber

1             Robert     Bangalore    9645612345

2             George    Chennai       9745612345

3             John        Bangalore    9845612345

Same data are in sharepoint list1(Customlist Name : Employeedatabase) also but exept PhoneNumber column.

 

So i need to add this Phone Number column to Employeedatabase custom list through External content type.

 

when i add this External Content Type to Employeedatabase custom list PhoneNumber column should be added and Based on that EMPID in that same row PhoneNumber should be update.

 

How i can achieve this through code without using sharepoint designer?

This is just example like that we are having more database with more columns.

Please anyone share sample code snippet or any link for this.

Thanks in advance.