SQL CASE语句,该如何处理

SQL CASE语句
表A,B,C中都有字段：Name，学号

问题：当A中Name不为空时，取A中的Name
  当B中Name不为空时，取B中Name
  其他情况去C中Name
 Name优先度：A>B>C
请教大侠这个SQL怎么写 ？？？？谢谢！

[解决办法]

SQL code

select isnull(isnull(a.name,b,name),c.name) as name   ,a.学号from a left join b on a.学号 = b.学号left join c on a.学号 = c.学号
[解决办法]
SQL code
select COALESCE(a.Name,b.Name,c.Name) as NameCOALESCE(a.学号,b.学号,c.学号) as 学号from a full join b on a.Name=b.Namefull join c on c.Name=a.Name
[解决办法]
case when
[解决办法]
SQL code
select  case when  a.name is not null then a.name  else  case when b.name is not null then b.name else c.name end endfrom  tb
[解决办法]
SQL code
select name=COALESCE(a.Name,b.Name,c.Name),a.学号from a left join b on a.学号 = b.学号left join c on a.学号 = c.学号