Why my selection between two dates in the same table doesn't work?

Question

I use SQL server 2014, i try the following query to select between two dates in the same table, the datatype is nvarchar, i executed the following query it just shows me three rows such('30/03/2015','30/04/2015','30/04/2015'),but in reality there is('29/02/2015','30/03/2015','31/04/2015','30/04/2015','30/04/2015')

select RegisteredDate
from Student
where Student.RegisteredDate between convert(nvarchar, '30/01/2014', 103)
    and convert(nvarchar, '30/04/2015', 103)

Answer 1

As i have read the other answers and comments, i could recommend you to firstly change the datatype of "RegisteredDate" from "nvarchar" to "date". Secondly use this standard 'yyyy-MM-dd' below code is what you need

select RegisteredDate 
from Student
where Student.RegisteredDate between '2014-01-30' and '2015-04-30'

you will not be in need of any conversions, this is how i do it for myself