exec sp_addtype schoolName, 'nvarchar(50)', 'not null'

exec sp_droptype schoolName

exec sp_help ac_test

create table ac_test1
(   Name varchar(30) null,
   Sex nchar(1) not null,
   Age Int   null
   )

Alter table ac_test1
alter constraint test_sex check (Sex=N'男'or Sex=N'女')

Alter table ac_test1
drop constraint test_sex

alter table ac_test1
alter column Sex nchar(1) not null;

insert into ac_test1 (name,sex,age) values('Mrs.Zhang',N'女',19);

insert into ac_test1 (name,age) values('Mrs.Zhang',19);

select * from ac_test1

delete from ac_test1

select len(sex),datalength(sex) from ac_test1

alter table ac_test1
add constraint default_sex default N'男' for Sex

exec sp_help ac_test1

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