Question

select regexp_replace('home care','home care','care') as column1,
       regexp_replace('home care','home care','home') as column2
  from WORDLIST w

输出：

column1 column2

 care    home

然后

select regexp_replace('care home','care home','home') as column3,
       regexp_replace('care home','care home','care') as column4
  from WORDLIST w

输出：

column3 column4

  home     care

因此，现在我想通过将一个选择语句嵌套到另一个没有“ join”字样且没有where子句的选择语句来将这两个正则表达式连接在一起，输出应如下所示：

column1 column2 column3 column4

  care   home  home     care

任何建议，我将不胜感激！

Answer 1

下面的代码应该可以工作，它确实使用了强制连接和'join on 1 = 1'

select
w1.column1
,w1.column2
,w2.column3
,w2.column4
from(
select regexp_replace('home care','home care','care') as column1, regexp_replace('home care','home care','home') as column2 from WORDLIST w
) as w1
left join (
select regexp_replace('care home','care home','home') as column3, regexp_replace('care home','care home','care') as column4 from WORDLIST w
) as w2 on 1 = 1

Answer 2

好吧，您可以尝试以下几种方法：

只需使用一个SELECT：

select regexp_replace('home care','home care','care') as column1,
       regexp_replace('home care','home care','home') as column2,
       regexp_replace('care home','care home','home') as column3,
       regexp_replace('care home','care home','care') as column4
  from WORDLIST w

使用交叉联接：

SELECT s1.COLUMN1,
       s1.COLUMN2,
       s2.COLUMN3,
       s2.COLUMN4 
  FROM (select regexp_replace('home care','home care','care') as column1,
               regexp_replace('home care','home care','home') as column2
        from WORDLIST) s1
  CROSS JOIN (select regexp_replace('care home','care home','home') as column3,
                     regexp_replace('care home','care home','care') as column4
                from WORDLIST) s2

请注意，根据WORDLIST中有多少行，这些查询返回的行可能会比您想要的多。 db<>fiddle here

您不妨考虑使用SELECT...FROM DUAL

有没有一种方法可以将一个选择语句嵌套到另一个选择语句？

2 个答案: