我试图在Oracle中创建一个CTE,它不从现有表中进行选择,而是将数据插入其中.目前,我正在创建一个表,然后在查询完成后删除它.有没有办法创建一个有效地做同样事情的CTE？这是我目前的代码：
- create table RTG_YEARS
- (YR date);
- insert into RTG_YEARS values (to_date('2013-01-01','yyyy-mm-dd'));
- insert into RTG_YEARS values (to_date('2013-12-31','yyyy-mm-dd'));
- insert into RTG_YEARS values (to_date('2014-01-01','yyyy-mm-dd'));
- insert into RTG_YEARS values (to_date('2014-12-31','yyyy-mm-dd'));
- insert into RTG_YEARS values (to_date('2015-01-01','yyyy-mm-dd'));
- insert into RTG_YEARS values (to_date('2015-12-31','yyyy-mm-dd'));
解决方法
您可以通过从dual中选择日期值来创建公用表表达式(CTE,subquery factoring等),并将它们组合在一起：
- with RTG_YEARS (YR) as (
- select to_date('2013-01-01','yyyy-mm-dd') from dual
- union all select to_date('2013-12-31','yyyy-mm-dd') from dual
- union all select to_date('2014-01-01','yyyy-mm-dd') from dual
- union all select to_date('2014-12-31','yyyy-mm-dd') from dual
- union all select to_date('2015-01-01','yyyy-mm-dd') from dual
- union all select to_date('2015-12-31','yyyy-mm-dd') from dual
- )
- select * from RTG_YEARS;
- YR
- ----------
- 2013-01-01
- 2013-12-31
- 2014-01-01
- 2014-12-31
- 2015-01-01
- 2015-12-31
与CTE无关,但您可以使用date literals减少输入：
- with RTG_YEARS (YR) as (
- select date '2013-01-01' from dual
- union all select date '2013-12-31' from dual
- union all select date '2014-01-01' from dual
- union all select date '2014-12-31' from dual
- union all select date '2015-01-01' from dual
- union all select date '2015-12-31' from dual
- )
- select * from RTG_YEARS;
