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with a as (
select 5 as n from dual
union all
select 10 from dual
union all
select 15 from dual
union all
select 20 from dual
)
select * from a where rownum=1 connect by rownum<6;
with a as (
select 5 as n from dual
union all
select 10 from dual
union all
select 15 from dual
union all
select 20 from dual
)
select * from a where rownum<6 connect by rownum=1;
with a as (
select 5 as n from dual
union all
select 10 from dual
union all
select 15 from dual
union all
select 20 from dual
)
select * from a where rownum<4 connect by level<6;
这一句的where又是筛选最后的结果的。
在这里面,where语句到底应该是在每一次循环作用,还是在最后才作用?