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Question

我有两张桌子：

person
id
name

car
name
person_id

目前查询如下：

SELECT
person.name
car.name
FROM
person, car
WHERE
person.id = car.person_id

现在，如果有人与某人相关联，这项工作正常。但是，如果没有，那么这个人就不会被退回。如果一个人没有车，我想在第'No Car'栏中返回包含car.name文字的行。

Answer 1

select person.name, coalesce(car.name, 'no car')
from person
left outer join car on person.id = car.person_id

Answer 2

SELECT person.name, CASE WHEN car.name IS NULL THEN 'no car' ELSE car.name END 
FROM person
LEFT JOIN car ON person.id = car.person_id

Answer 3

select person.name, ISNULL(car.name, 'no car')
from person
left join car on person.id = car.person_id