[英]SQL: SELECT where 2 columns from different tables are the same
这是带有多个joins
的一个选项:
select p1.pres_name, p2.pres_name, ph.hobby
from pres_mar p1
join pres_mar p2 on p1.pres_name != p2.pres_name and p1.mar_year = p2.mar_year
join pres_hob ph on p1.pres_name = ph.pres_name
join pres_hob ph2 on p2.pres_name = ph2.pres_name and ph.hobby = ph2.hobby
根据您的预期结果, exists
另一个使用方法:
select pm.pres_name, ph.hobby
from pres_mar pm
join pres_hob ph on pm.pres_name = ph.pres_name
where exists (
select 1
from pres_mar pm2
join pres_hob ph2 on pm2.pres_name = ph2.pres_name
where pm.pres_name != pm2.pres_name and
ph.hobby = ph2.hobby
)
这听起来像是一个糟糕的数据库架构,我假设它是出于学习目的,无论如何,您可以做类似的事情
SELECT
h.name,
h.hobby,
m.year
FROM
pres_hob h,
pres_mar m
WHERE
h.hobby = 'tennis'
AND
m.year = 2016
对于每位拥有2016年结婚年和网球爱好的总统,这将返回1项记录。
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