What is Column level Encryption in sql server 2005 ?

use hello

if not exists(select * from sys.symmetric_keys where name='##MS_DATABASEMASTERKEY##')
create master key
encryption by password='Annai1!'
go
select * from sys.certificates

if not exists(select * from sys.certificates where name='cert246')
create certificate cert246
with subject='certi for sam'
go



create symmetric key sym246
with algorithm=AES_256
encryption by certificate cert246
go
create table sam
(
name varchar(20),
ssn varbinary(256)
)
go

create view sam_decry
as


select name,
convert(nvarchar,DecryptByKey(ssn)) as "ssn"
from sam

go

create trigger trig246
on sam_decry
instead of insert
as
begin
open symmetric key sym246
decryption by certificate cert246;

insert into sam(name,ssn)
select
i.name,
EncryptByKey(Key_GUID('sym246'),ssn)from inserted i

end


-----------------\\


insert into sam_decry
values('sudan','madhuxyu')

select * from sam

select * from sam_decry