SQL - UNION不下令第二选择

Question

我真的试图解决这一难题： https://www.hackerrank.com/challenges/the-pads

我的解决办法是这样的在MySQL：

(SELECT CONCAT(Name,'(',SUBSTR(Occupation,1,1),')') FROM Occupations ORDER BY Name) 
UNION 
(SELECT CONCAT('There are total ', COUNT(Occupation), ' ',LOWER(Occupation),'s.') AS total FROM Occupations 
GROUP BY Occupation 
ORDER BY total); 

但是它没有ORDER BY总。

Ashley(P) 
Samantha(A) 
Julia(D) 
Britney(P) 
Maria(P) 
Meera(P) 
Priya(D) 
Priyanka(P) 
Jennifer(A) 
Ketty(A) 
Belvet(P) 
Naomi(P) 
Jane(S) 
Jenny(S) 
Kristeen(S) 
Christeen(S) 
Eve(A) 
Aamina(D) 
There are total 4 actors. 
There are total 3 doctors. 
There are total 7 professors. 
There are total 4 singers. 

如果我只运行

SELECT CONCAT('There are total ', COUNT(Occupation), ' ',LOWER(Occupation),'s.') AS total FROM Occupations 
GROUP BY Occupation 
ORDER BY total 

它顺序：

There are total 3 doctors. 
There are total 4 actors. 
There are total 4 singers. 
There are total 7 professors. 

Answer 1

这是正确的。结果集的排序仅基于在最外面的order by。 union对于其他操作也是如此。

(SELECT CONCAT(Name,'(', SUBSTR(Occupation,1,1),')') AS total 
FROM Occupations 
ORDER BY Name 
) 
UNION ALL 
(SELECT CONCAT('There are total ', COUNT(Occupation), ' ', LOWER(Occupation), 's.') AS total 
FROM Occupations 
GROUP BY Occupation 
) 
ORDER BY (CASE WHEN total LIKE 'There are total%' THEN 1 ELSE 0 END), 
     Total; 

这假定Name从未与'There are total'开始，这可能看起来。

Answer 2

@gordon答案是罚款

但你必须创建一个“虚拟”字段每个组单独一个更通用的情况。

(SELECT CONCAT(Name,'(', SUBSTR(Occupation,1,1),')') as Name, 
     0 as dummy 
FROM Occupations 
) 
UNION ALL 
(SELECT CONCAT('There are total ', COUNT(Occupation), ' ', LOWER(Occupation), 's.') AS Name, 
     1 as dummy 
FROM Occupations 
GROUP BY Occupation 
) 
ORDER BY dummy, name 

Answer 3

结果得到由最终ORDER BY条款订购。这是ORDER BY total，即第一列。 （你只在UNION的第二部分给出这个名字，这可能不适用于另一个DBMS，你应该在第一部分的UNION查询中命名你选择的列。）

你想先取得名字，然后聚合。然后按字母顺序排列名称，按字母顺序汇总（即不是按字母顺序排列，不是1→10→11→2→20→1→​​2→10→11→20。 ）然后按工作名称。您可以为此任务创建分类键。我假设你真的想要UNION ALL，而不是UNION。如果我错了，基于答案改变它:-)

SELECT txt 
FROM 
(
    SELECT 
    CONCAT(Name, '(', SUBSTR(Occupation, 1, 1), ')') as txt, 
    1 as sortkey1, 
    CONCAT(Name, '(', SUBSTR(Occupation, 1, 1), ')') as sortkey2 
    FROM Occupations 
    UNION ALL 
    SELECT 
    CONCAT('There are total ', COUNT(Occupation), ' ', LOWER(Occupation), 's.') AS txt, 
    2 + COUNT(Occupation) as sortkey1, 
    LOWER(Occupation) as sortkey2 
    FROM Occupations 
    GROUP BY Occupation 
) data 
ORDER BY sortkey1, sortkey2; 

Answer 4

和我最了解我来到这个解决方案，对于这种情况下的工作原理：

(SELECT CONCAT(Name,'(',SUBSTR(Occupation,1,1),')') as total FROM Occupations ORDER BY Name) 
UNION ALL 
(SELECT CONCAT('There are total ', COUNT(Occupation), ' ',LOWER(Occupation),'s.') AS total FROM Occupations 
GROUP BY Occupation) 
ORDER BY total;