多级级联内部联接选择查询

Question

我想从short_name(国家名称)、name(州表)或region_name的任何可用数据中选择post_id。对region_name而不是short_name(国家名称)，name(州表)执行以下查询，结果为真。

select *
from t_post_city
inner join t_region on t_region.region_id = t_post_city.city_id
inner join t_country on t_region.country_id = t_country.country_id
inner join t_states on t_region.province_id = t_states.state_id
where t_country.short_name like %india%
   or t_states.name like %rajasthan%
   or t_region.region_name like %sitapura%

请告诉我，我哪里弄错了！

Answer 1

对三个条件中的每一个都使用不同的表表达式。在 SQL 中使用联合编写 OR 逻辑：

select post_id
from t_post_city
inner join t_region on t_region.region_id = t_post_city.city_id
where t_country.short_name like %india%
t_region.region_name like %sitapura%
union
select post_id
from t_post_city
inner join t_region on t_region.region_id = t_post_city.city_id
inner join t_country on t_region.country_id = t_country.country_id
where t_country.short_name like %india%
union
select post_id
from t_post_city
inner join t_region on t_region.region_id = t_post_city.city_id
inner join t_states on t_region.province_id = t_states.state_id
where t_states.name like %rajasthan%;

Answer 2

select *
from t_post_city
LEFT OUTER join t_region on t_region.region_id = t_post_city.city_id
LEFT OUTER join t_country on t_region.country_id = t_country.country_id
LEFT OUTER join t_states on t_region.province_id = t_states.state_id
 where t_country.short_name like '%india%'
 or t_states.name like '%rajasthan%'
 or t_region.region_name like '%sitapura%'