关于oracle with as用法

1 2 3 4 5 6 7 8 9 --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;

其实就是把一大堆重复用到的sql语句放在with as里面，取一个别名，后面的查询就可以用它，这样对于大批量的sql语句起到一个优化的作用，而且清楚明了。

向一张表插入数据的with as用法

1 2 3 4 5 insert? into? table2with????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...;

select s1.sid,s2.sid from s1,s2需要有关联条件，不然结果会是笛卡尔积。
with as 相当于虚拟视图。

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副标题[/!--empirenews.page--] with as语法 –针对一个别名 with tmp as (select * from tb_name) –针对多个别名 with ?? tmp as (select * from tb_name), ?? tmp2 as (select * from tb_name2), ?? tmp3 as (select * from tb_name3), ?? …