When on the client side you specify co/coro/combo columns (combo-box/select) in the grid, the grid will automatically request data for them in the same manner as for filtering options.
By default, the grid will use DISTINCT select against the related field, and fetch all possible options.
If you need to define a custom list of options, you can use one of 2 ways:
HashMap<String,String> c2 = new HashMap<String,String>();
c2.put("91", "one");
c2.put("75", "two");
grid.set_options("item_nm",c2);
BaseConnector options = new OptionsConnector(conn);
options.render_table("countries","item_id","item_id(value),item_nm(label)");
grid.set_options("item_nm",options);
co/combo type
coro type: