How to display all data with nulls using Pivot [duplicate] - oracle

Question

please help me solve this problem:
You are given a table, containing two columns:
column is one of the followings:
Doctor
Professor
Singer
Actor
Write a query to output the names underneath the corresponding occ. in the following format:
+--------+-----------+--------+------+
| Doctor | Professor | Singer | Actor|
+--------+-----------+--------+------+
Names must be listed in alphabetically sorted order.
Sample Input
Name Occupation
Meera Singer
Ashely Professor
Ketty Professor
Christeen Professor
Jane Actor
Jenny Doctor
Priya Singer
Sample Output
Jenny Ashley Meera Jane
Samantha Christeen Priya Julia
NULL Ketty NULL Maria
Note
Print "NULL" when there are no more names corresponding to an occupation.
I tried using :
SELECT *
FROM
(
SELECT [Name], [Occupation]
FROM occupations
) AS source
PIVOT
(
max([Name])
FOR [occupation] IN ([Doctor], [Professor], [Singer], [Actor])
) as pvt;
which gives the following output:
Priya Priyanka Kristeen Samantha
How to fix it ?

Answer 1

You just need to give each name a row number based on their occupation and order alphabetically.. then include that row number in your pivot query.
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
-- Edit: We need to enclose the subquery after PIVOT within parenthesis "()" to make it work on SQL Server.

Answer 2

I tried this in Oracle, seemed easier to comprehend:
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

Here is the MYSQL version of the answer. Little difficult because of no presence of FULL OUTER JOIN in HACKERRANK.com
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;