在视图中建个源表中没有，但根据源表计算出来的字段

[aloneone]

table1
zlbm char(10)
......
//-------------------------------

table2:
zlbm char(10)
......
//-------------------------------

View1:从table1中取若干字段，另加一逻辑字段YN，当table1.zlbm在table2中出现时，YN的值为T，否则为F。

[caiyunxia]

select table1.*,(case when table2.zlbm is null then 'f' else 't' end ) as yn
from table1 left join table2 on table1.zlbm=table2.zlbm

[yujohny]

同意caiyunxia(monkey)

[caiyunxia]

select * ,case when (select top 1 zlbm from table2 where zlbm=table1.zlbm) is not null then 't' else 'f' end as yn
from table1

[dafu71]

select table1.*, 'T' as YN from table1 where exists (select 1 from table2 where table1.zlbm=table2.zlbm)
union
select table1.*, 'F' as YN from table1 where not exists (select 1 from table2 where table1.zlbm=table2.zlbm)

[aloneone]

三种方法我都试成功了，再多问一个问题，哪种方法的效率高些呢？

[aloneone]

没人回答？我结贴算了。