1.update statistics [表名] 更新表的统计信息
2.Case When
(参考：http://www.cnblogs.com/yaozhenpeng/p/6796692.html)
select name ,
valiad=case valiad when 'Y' THEN '有效' when 'N' then ''无效 else '' end
from table1
3.级联更新、级联删除
级联更新：
update S1
set S1.Name=S2.Name
from A表 as S1,B表 as S2
where S1.ID=S2.id
级联删除:
delete S1
FROM A AS S1,B AS S2
WHERE S1.ID=S2.ID
4.首行缩进
shift+Tab(多行)