oracle with as用法

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--相当于建了个e临时表

with e as (select * from scott.emp e where e.empno=7499)

select * from e;

--相当于建了e、d临时表

with

     e as (select * from scott.emp),

     d as (select * from scott.dept)

select * from e, d where e.deptno = d.deptno;

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insert into table2

with

    s1 as (select rownum c1 from dual connect by rownum <= 10),

    s2 as (select rownum c2 from dual connect by rownum <= 10)

select a.c1, b.c2 from s1 a, s2 b where...;

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with

    sql1 as (select to_char(a) s_name from test_tempa),

    sql2 as (select to_char(b) s_name from test_tempb where not exists (select s_name from sql1 where rownum=1))

select * from sql1

union all

select * from sql2

union all

select ‘no records‘ from dual

       where not exists (select s_name from sql1 where rownum=1)

       and not exists (select s_name from sql2 where rownum=1);