How to change data type from date to int in SQL Server 2012?

Question

I have a table like

CREATE TABLE Student 
(
    s_id int NOT NULL IDENTITY(1,1),
    sname nvarchar(30) NOT NULL,
    address nvarchar(30) NOT NULL,
    gender varchar(10) NOT NULL,
    birthyear date NOT NULL,
    CONSTRAINT PK_Student PRIMARY KEY (s_id)
);

Now I want to change data type of column birthyear from date to integer.

I followed tutorial of w3school.com :

ALTER TABLE table_name
ALTER COLUMN column_name datatype

Here is my code:

ALTER TABLE Student 
ALTER COLUMN birthyear int

But it throws an error

Operand type clash: date is incompatible with int

Can you people help me? Please.

Thank you!

Answer 1

When column is empty (all NULLs) you can make transitional step by using varchar conversion. Direct conversion is not possible, but this should work:
date -> varchar -> int

ALTER TABLE Student ALTER COLUMN birthyear varchar(200);
ALTER TABLE Student ALTER COLUMN birthyear int;

See this answer.