嵌套選擇查詢 - mysql sakila數據庫

Question

我已經找到每個地區的最小後綴，現在想要找到所有這些地區郵政編碼最小值的最大值。我陷入瞭如何做最大值的同時保持其他部分不變。

select 
    district, 
    postal_code, 
    min(postal_code) from address 
group by district 
having district is not null and district !="" and postal_code>0 
order by district; 

Answer 1

如果只需要max(min_postal_code)，使用下面的語句。

select max(min_postal_code) 
from (
    select district, min(postal_code) AS min_postal_code 
    from address 
    where district is not null and district !="" and postal_code>0 
    group by district 
    order by district) t 

如果區域名稱與MAX(min_postal_code)也需要。使用以下語句。

select * 
from (select district, min(postal_code) AS min_postal_code 
    from address 
    where district is not null and district !="" and postal_code>0 
    group by district) t 
where t.min_postal_code = 
(
    select max(min_postal_code) 
    from (select district, min(postal_code) AS min_postal_code 
     from address 
     where district is not null and district !="" and postal_code>0 
     group by district) t2 
);