我认为您必须进行子选择才能获得结果:

I think you have to do a subselect to get your result:

SELECT groceries.product, person.name, location.name
FROM person
LEFT JOIN groceries ON person.id = groceries.person_id
LEFT JOIN location ON person.id = location.person_id
WHERE person.id
IN (
SELECT person.id
FROM person
LEFT JOIN groceries ON person.id = groceries.person_id
LEFT JOIN location ON person.id = location.person_id
GROUP BY person.id
HAVING count( person.id ) =1
)