题解 | #when按城市排序,如果城市为空，则按国家排序#
请按城市对客户进行排序,如果城市为空，则按国家排序
https://www.nowcoder.com/practice/c1b1d5bd008b4797ab2ef53a3afc4aba
#两种方式：if和when
#if
#select customer_id,gender,city,country,age,latest_place_order_date from `customers_info` order by (if(city is not null,city,country))
#when
select customer_id,gender,city,country,age,latest_place_order_date from `customers_info` order by (case
when city is null then country
else city
end)
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