[英]Join two select statements sql
我有两个希望通过自然连接加入的sql语句,但是由于某些原因,以下内容给了我一个错误:
(select city_name
from city
left join country
on country.country_name=city.country_name
where country.continent='Europe'
and city.iscapitol='yes')
natural join
(select city_name
from city
left join country
on country.country_name=city.country_name
where country.continent='Europe'
and city.iscapitol='no';)
我正在使用oracle平台,它抛出的错误是:
natural join
*
ERROR at line 7:
ORA-00933: SQL command not properly ended
出现此错误的原因是什么? 任何帮助将不胜感激。
select * from (
(select city_name
from city
left join country
on country.country_name=city.country_name
where country.continent='Europe'
and city.iscapitol='yes')
natural join
(select city_name
from city
left join country
on country.country_name=city.country_name
where country.continent='Europe'
and city.iscapitol='no'))
我已经搬走了;
并添加了外部查询。 我还建议用明确的join
条件替换natural join
join
with eurcities as (select city_name, iscapitol, country_name from city
left join country on country.country_name=city.country_name
where country.continent='Europe')
select c1.city_name, c2.city_name, c1.country_name
from eurcities c1 inner join eurcities c2 on (c1.country_name = c2.country_name)
where c1.iscapitol = 'yes' and c2.iscapitol = 'no';
如果没有with
它看起来像:
select c1.city_name, c2.city_name, c1.country_name
from (select city_name, iscapitol, country_name from city
left join country on country.country_name=city.country_name
where country.continent='Europe') c1
inner join (select city_name, iscapitol, country_name from city
left join country on country.country_name=city.country_name
where country.continent='Europe') c2
on (c1.country_name = c2.country_name)
where c1.iscapitol = 'yes' and c2.iscapitol = 'no';
首先,不学习natural join
。 这是一个等待发生的错误。 在代码中不显示join
键很危险。 忽略声明的外键关系是不明智的。 依赖命名约定很尴尬。
您可以通过写这个using
。 因此,修复语法,如下所示:
select *
from (select city_name
from city left join
country
on country.country_name = city.country_name
where country.continent='Europe' and city.iscapitol = 'yes'
) cc join
(select city_name
from city left join
country
on country.country_name = city.country_name
where country.continent = 'Europe' and city.iscapitol='no'
) cnc
using (city_name);
请注意,子查询中的left join
s是不必要的。
就是说,我认为聚合是一种更简单的查询方法:
select city_name
from city join
country
on country.country_name = city.country_name
where country.continent = 'Europe'
having sum(case when city.iscapitol = 'yes' then 1 else 0 end) > 0 and
sum(case when city.iscapitol = 'no' then 1 else 0 end) > 0;
或者,如果iscapitol
[原文]只需要两个值,您可以使用此为having
条款:
having min(city.iscapitol) <> max(city.iscapitol)
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