求一更新语句

[lvxianda]

tbCategory表
categoryID categoryName
1 a
2 b

tbItem表
itmeID itemName categoryID
1 aaa 1
2 bbb 1
3 ccc 2

我想将tbCategory表中categoryName = a的数据 在tbItem表中对应的itemName 的内容前面加一个 * 号
希望结果如下
tbItem表
itmeID itemName categoryID
1 *aaa 1
2 *bbb 1
3 *ccc 2

[AcHerat]

select itemID,(case when categoryID in (select categoryID from tbCategory where categoryname = 'a')
                    then '*' + itemname else itemname end)itemname,categoryID
from tbItem

[AcHerat]

update tbItem
set categoryName = '*' + categoryName
where categoryID in (select categoryID from tbCategory where categoryname = 'a')

[快溜]

update tbItem set itemName='*'+itemName

[htl258_Tony]

update b set b.itemName ='*'+b.itemName 
from tbCategory a,tbItem b
where a.categoryID =b.categoryID 

[Music杰]

categoryname = 'a'好像不能给死的吧！