As in SQL you can insert more than row you can making your string like that
INSERT INTO 'tablename' ('column1') VALUES
('val1'),
('val2'),
('val2'),
('val2');
and here implementation of insertion code :
public void diff_date(View v){
SimpleDateFormat sdf = new SimpleDateFormat( "yyyy-MM-dd" );
String insertRows = "INSERT INTO 'tablename' ('column1') VALUES";
String date_in = sdf.format( dateAndTime .getTime() );
String date_out = sdf.format( dateAndTime1.getTime() );
int differenza_date = Days.daysBetween(new DateTime(date_in), new DateTime(date_out)).getDays();
for(int i=1 ; i < differenza_date ; i++)
{
// increase i day each time and save it in string
insertRows += "("+increasedDate+"),"
}
// and here insert into database
db.execSQL(insertRows)
}