Dependent Dropdown in SugarCRM (SugarCE)

In order to make dependent dropdown, first you need to create 2 independent dropdown list from sugar admin panel. Let's say country_c and city_c with Item Name as below:

For country_c menu:
Item Name                    Display Name
AAA                             Thailand
BBB                              Nepal

For city_c menu:
Item Name                   Display Name
AAA_1                        Bangkok
AAA_2                        Phuket
BBB_1                         Lumbini
BBB_2                         Pokhara

Here you can see that if Item Name for country is AAA then the corresponding Item Name for city is AAA_1, AAA_2 i.e. it starts with AAA.