改数据结构：alter table pyz change xb xingbie char(2)哪里错了？

[pyz8000]

表名： pyz
字段：xm char(10),xb char(10)
把
xm 改成 xingming char(10)
xb 改成 xingbie char(2)

[pyz8000]

????????????????????

[xiyahui]

alter table stu
alter column xb char(2)

[mjhnet]

alter table pyz add xingming char(10),xingbie char(2)

update pyz set xingming = xm , xingbie = xb

alter table drop column xm , xb

[pengdali]

exec sp_rename 'pyz.xm','xingming'

go
alter table pyz add xingbie char(2)

update pyz set xingbie=left(xb,2)

alter table drop column xb