如何在 sql server 中使用数据透视（没有聚合）？

Question

请帮我解决这个问题： 您将获得一个包含两列的表格： 列是以下之一：

Doctor
Professor
Singer
Actor

写一个查询输出对应occ下面的名字。格式如下：

+--------+-----------+--------+------+

| Doctor | Professor | Singer | Actor|

+--------+-----------+--------+------+

姓名必须按字母顺序排列。

示例输入

Name        Occupation
Meera       Singer
Ashely      Professor
Ketty       Professor
Christeen   Professor
Jane        Actor
Jenny       Doctor
Priya       Singer    

样本输出

Jenny    Ashley     Meera  Jane

Samantha Christeen  Priya  Julia

NULL     Ketty      NULL   Maria

注意

当没有更多与职业对应的名称时，打印“NULL”。

我尝试使用：

SELECT *
FROM
(
SELECT [Name], [Occupation] 
FROM occupations 
) AS source
PIVOT
(
    max([Name])
    FOR [occupation] IN ([Doctor], [Professor], [Singer], [Actor]) 
) as pvt;

给出以下输出：

Priya Priyanka Kristeen Samantha 

如何解决？

Answer 1

您只需要根据每个名称的职业和字母顺序为每个名称指定一个行号。然后在您的数据透视查询中包含该行号。

CREATE TABLE Occupations (
     NAME VARCHAR(MAX),
     Occupation VARCHAR(MAX)
    )
INSERT  INTO Occupations
VALUES
        ('Samantha','Doctor'),
        ('Julia','Actor'),
        ('Maria','Actor'),
        ('Meera','Singer'),
        ('Ashley','Professor'),
        ('Ketty','Professor'),
        ('Christeen','Professor'),
        ('Jane','Actor'),
        ('Jenny','Doctor'),
        ('Priya','Singer');

SELECT
    [Doctor],
    [Professor],
    [Singer],
    [Actor]
FROM
    (SELECT 
         ROW_NUMBER() OVER (PARTITION BY Occupation ORDER BY Name) rn,
         [Name],
         [Occupation] 
     FROM 
         Occupations
    ) AS source 
PIVOT
    MAX(Name) FOR [occupation] IN ([Doctor],[Professor],[Singer],[Actor]) as pvt
ORDER BY rn


DROP TABLE Occupations

Answer 2

我在 Oracle 中试过这个，似乎更容易理解：

SELECT min(Doctor), min(Professor), min(Singer), min(Actor)
FROM
( Select
ROW_NUMBER() OVER (PARTITION BY Occupation order by Name) rn, 
CASE 
WHEN Occupation = 'Doctor' then Name
end as Doctor,
CASE 
WHEN Occupation = 'Professor' then Name
end as Professor,
CASE 
WHEN Occupation = 'Singer' then Name
end as Singer,
CASE 
WHEN Occupation = 'Actor' then Name
end as Actor
from OCCUPATIONS
order by Name) a
group by rn
order by rn;

Answer 3

SELECT [Doctor], [Professor], [Singer], [Actor] FROM   
(
    SELECT ROW_NUMBER() OVER (PARTITION BY Occupation ORDER BY Name) ROW_NO, 
    ISNULL(NULL,Name) as Name, Occupation
    FROM Occupations
) AS t 
PIVOT(
    MAX(Name)
    FOR Occupation IN (
        [Doctor], 
        [Professor], 
        [Singer], 
        [Actor]
    )
) AS pivot_table
ORDER BY ROW_NO;

Answer 4

这是答案的 MYSQL 版本。由于 HACKERRANK.com 中不存在 FULL OUTER JOIN，所以难度不大

SET @r1=0, @r2 = 0, @r3 = 0, @r4 = 0;

SELECT t1.name, t2.name, t3.name, t4.name
FROM

(SELECT 
    (@r1:=@r1 + 1) AS num1, 
    Name
FROM
    Occupations
    WHERE Occupation = 'Doctor'
ORDER BY Name) as t1

RIGHT JOIN

(SELECT 
    (@r2:=@r2 + 1) AS num2, 
    Name
FROM
    Occupations
    WHERE Occupation = 'Professor'
ORDER BY Name) as t2

ON t1.num1 = t2.num2

LEFT JOIN

(SELECT 
    (@r3:=@r3 + 1) AS num3, 
    Name
FROM
    Occupations
    WHERE Occupation = 'Singer'
ORDER BY Name) as t3

ON t2.num2 = t3.num3

LEFT JOIN

(SELECT 
    (@r4:=@r4 + 1) AS num4, 
    Name
FROM
    Occupations
    WHERE Occupation = 'Actor'
ORDER BY Name) as t4

ON t2.num2 = t4.num4

Answer 5

SET @r1=0, @r2=0, @r3 =0, @r4=0;
SELECT MIN(Doctor), MIN(Professor), MIN(Singer), MIN(Actor) FROM
(SELECT CASE Occupation WHEN 'Doctor' THEN @r1:=@r1+1
                       WHEN 'Professor' THEN @r2:=@r2+1
                       WHEN 'Singer' THEN @r3:=@r3+1
                       WHEN 'Actor' THEN @r4:=@r4+1 END
       AS RowLine,
       CASE WHEN Occupation = 'Doctor' THEN Name END AS Doctor,
       CASE WHEN Occupation = 'Professor' THEN Name END AS Professor,
       CASE WHEN Occupation = 'Singer' THEN Name END AS Singer,
       CASE WHEN Occupation = 'Actor' THEN Name END AS Actor
       FROM OCCUPATIONS ORDER BY Name) AS t
GROUP BY RowLine;