Select value as column - sql

Question

If I have a table containing:
game powerup used
memory 1 12
memory 2 10
bejeweled 2 88
bejeweled 3 54
...where the (number of) different possible values of powerup are unknown, is there a way to SELECT this as something like
game 1_used 2_used 3_used
memory 12 10
bejeweled 88 54
I'm interested in pure SQL or PostgreSQL answers.
Note: This is an academical question, I don't have a use case at the moment. Answer it for your enjoyment or for the good of the site, not my personal benefit :)

Answer 1

Try this one:
SELECT game
,MAX(CASE WHEN powerup = 1 THEN used ELSE NULL END) AS used1
,MAX(CASE WHEN powerup = 2 THEN used ELSE NULL END) AS used2
,MAX(CASE WHEN powerup = 3 THEN used ELSE NULL END) AS used3
FROM Table1
GROUP BY game;
Output:
╔═══════════╦════════╦═══════╦════════╗
║ GAME ║ USED1 ║ USED2 ║ USED3 ║
╠═══════════╬════════╬═══════╬════════╣
║ bejeweled ║ (null) ║ 88 ║ 54 ║
║ memory ║ 12 ║ 10 ║ (null) ║
╚═══════════╩════════╩═══════╩════════╝
See this SQLFiddle

Answer 2

DROP SCHEMA tmp CASCADE;
CREATE SCHEMA tmp ;
SET search_path=tmp;
CREATE TABLE meuk
( game varchar
, powerup INTEGER NOT NULL
, used INTEGER NOT NULL
, PRIMARY KEY (game,powerup)
);
INSERT INTO meuk(game, powerup, used) VALUES
( 'memory' , 1,12)
,( 'memory' , 2,10)
,( 'bejeweled' , 2,88)
,( 'bejeweled' , 3,54)
;
-- using a self-join as
-- a poor man's pivot.
WITH dom AS (
SELECT DISTINCT game AS game
FROM meuk
)
SELECT m0.game AS game
, m1.used AS used_1
, m2.used AS used_2
, m3.used AS used_3
FROM dom m0
LEFT JOIN meuk m1 ON m1.game = m0.game AND m1.powerup = 1
LEFT JOIN meuk m2 ON m2.game = m0.game AND m2.powerup = 2
LEFT JOIN meuk m3 ON m3.game = m0.game AND m3.powerup = 3
;
RESULTS:
game | used_1 | used_2 | used_3
-----------+--------+--------+--------
bejeweled | | 88 | 54
memory | 12 | 10 |
(2 rows)

Answer 3

CREATE TABLE test_1
( game varchar(10)
, powerup INTEGER NOT NULL
, used INTEGER NOT NULL
);
INSERT INTO test_1(game, powerup, used)
SELECT 'memory' , 1,12 UNION ALL
SELECT 'memory' , 2,10 UNION ALL
SELECT 'bejeweled' , 2,88 UNION ALL
SELECT 'bejeweled' , 3,54
select * from test_1
DECLARE #COLUMNS varchar(max)
SELECT #COLUMNS = COALESCE(#COLUMNS+'],[' ,'') + CAST(powerup as varchar)
FROM test_1
GROUP BY powerup
SET #COLUMNS = '[' + #COLUMNS + ']'
EXECUTE ('select * from test_1
pivot (SUM(used) for powerup IN ('+ #COLUMNS +')) as used_t')