[英]SQL: SELECT where 2 columns from different tables are the same
這是帶有多個joins
的一個選項:
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
根據您的預期結果, exists
另一個使用方法:
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
)
這聽起來像是一個糟糕的數據庫架構,我假設它是出於學習目的,無論如何,您可以做類似的事情
SELECT
h.name,
h.hobby,
m.year
FROM
pres_hob h,
pres_mar m
WHERE
h.hobby = 'tennis'
AND
m.year = 2016
對於每位擁有2016年結婚年和網球愛好的總統,這將返回1項記錄。
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