select null a from t1返回的值和select a from t1 where 0=1返回的值是否一致？
select * from t2 where t2.a not in (select null a from t1)
和
select * from t2 where t2.a not in (select a from t1 where 0=1)
和
select * from t2 where t2.a not in (select a from t1 where t1.a like 'kkkk')
--select a from t1 where t1.a like 'kkkk' 返回的值也是空值。
是否有区别？
我现在碰到的问题是：
select * from t2 where t2.a not in (select a from t1 where t1.a like 'kkkk')
返回的值一会是空，一会儿有结果。
不明白是怎么啦？
个人觉得是oracle 的bug!
