负号运算符和不存在结果在oracle中相同的结果

Question

任何人都可以帮助确认，在oracle减运算符和不存在返回相同的结果集吗？

问候， Mayuran

Answer 1

这里的证明，负和不存在的查询不返回相同的结果：

减查询

with t1 as (select 1 id, 'a' val from dual union all 
      select 1 id, 'a' val from dual union all 
      select 2 id, 'b' val from dual), 
    t2 as (select 2 id, 'b' val from dual union all 
      select 3 id, 'c' val from dual) 
select id, val 
from t1 
minus 
select id, val 
from t2; 

减结果

 ID VAL 
---------- --- 
     1 a 

NOT EXISTS查询

with t1 as (select 1 id, 'a' val from dual union all 
      select 1 id, 'a' val from dual union all 
      select 2 id, 'b' val from dual), 
    t2 as (select 2 id, 'b' val from dual union all 
      select 3 id, 'c' val from dual) 
select id, val 
from t1 
where not exists (select null 
        from t2 
        where t1.id = t2.id 
        and t1.val = t2.val); 

NOT EXISTS结果

 ID VAL 
---------- --- 
     1 a 
     1 a