Question

我将非常感谢帮助找到如何使用WHERE和IN作为要求组合/加入两个简单SQL查询的方法。

简单地说，我想要这个查询的结果：

SELECT Nationality, MAX(ActorName) as Oldest,
FROM ACTOR 
WHERE BirthDate IN
(SELECT MIN(BirthDate) as MinBday FROM ACTOR GROUP BY Nationality)
GROUP BY Nationality

结果如下：

+------------+--------------+
| nationality| oldest       |
+------------+--------------+
| american   | brad pitt    |
+------------+--------------+
| british    | pierce bro   |
+------------+--------------+
| italian    | monica bellu |
+------------+--------------+

加入此查询的结果：

SELECT Nationality, MAX(ActorName) as Oldest,
FROM ACTOR 
WHERE BirthDate IN
(SELECT MAX(BirthDate) as MinBday FROM ACTOR GROUP BY Nationality)
GROUP BY Nationality

结果如下：

+------------+--------------+
| nationality| youngest     |
+------------+--------------+
| american   | angelina j   |
+------------+--------------+
| british    | jason stat   |
+------------+--------------+
| italian    | paul gia     |
+------------+--------------+

为了得到如下结果表：

+------------+--------------+--------------+
|nationality | oldest       | youngest     |
+------------+--------------+--------------+
| american   | brad pitt    | angelina j   |
+------------+--------------+--------------+
| british    | pierce bro   | jason stat   |
+------------+--------------+--------------+
| italian    | monica bellu | paul gia     |
+------------+--------------+--------------+

注意：对于最早的出生日期，2个查询之间的唯一区别是 MIN （出生日期），而对于最年初的出生日期， MAX （出生日期）。

Answer 1

您可以获得生日，并可以直接加入

SELECT a.Nationality, MAX(a.ActorName) as Oldest,
FROM ACTOR a
JOIN (SELECT Nationality, 
 MIN(BirthDate) as MinBday,
 MAX(BirthDate) as MaxBday
  FROM ACTOR 
  GROUP BY Nationality) xxx
ON a.Nationality = xxx.Nationality
AND (a.BirthDate = xxx.MinBday OR a.BirthDate = xxx.MaxBday)
GROUP BY Nationality;

Answer 2

一个非常丑陋的sql可以跟随，而不是最有效的，只是一种方法。

SELECT
    t1.Nationality, t1.Oldest, t2.youngest
FROM (
    SELECT Nationality, MAX(ActorName) as Oldest -- ,
    FROM ACTOR 
    WHERE BirthDate IN
    (SELECT MIN(BirthDate) as MinBday FROM ACTOR GROUP BY Nationality)
    GROUP BY Nationality
) t1
JOIN (
    SELECT Nationality, MAX(ActorName) as youngest
    FROM ACTOR 
    WHERE BirthDate IN
    (SELECT MAX(BirthDate) as MaxBday FROM ACTOR GROUP BY Nationality)
    GROUP BY Nationality
) t2 ON t1.Nationality = t2.Nationality

或试试这个（未经测试）：

SELECT 
    Nationality, 
    MAX(CASE WHEN BirthDate = t1.MinBday THEN ActorName ELSE NULL END) as Oldest,
    MAX(CASE WHEN BirthDate = t1.MaxBday THEN ActorName ELSE NULL END) as youngest
FROM ACTOR
JOIN (
    SELECT Nationality, MIN(BirthDate) as MinBday, MAX(BirthDate) as MaxBday
    FROM ACTOR GROUP BY Nationality) t
ON ACTOR.Nationality = t.Nationality
GROUP BY Nationality

通过追加新列来加入两个不同的MySQL结果查询

2 个答案: