if object_id('tb') is not null drop table tb
create table tb(F1 varchar(10),id int) ----测试数据
insert tb select 'C',5
insert tb select 'A',1
insert tb select 'A',2
insert tb select 'B',1
insert tb select 'B',4
insert tb select 'B',7
insert tb select 'C',7
insert tb select 'C',5
请手写出如下语句的答案,并对第一条语句的执行顺序和结果进行剖析.
1.select * from tb a where exists(select * from tb where F1=a.F1 and id<a.id)
2.select * from tb a where id in (select id from tb where F1=a.F1 and id<a.id)
3.select distinct * from tb a where not exists(select 1 from tb where F1=a.F1 and id<a.id)
