Обсуждение: matrix query?

this is probably a more generic SQL question than a postgres specific one, but:


CREATE TABLE data
(
customer  varchar(10),
widgets   int,
day       int
);

INSERT INTO DATA values('CustA', 5, 1);
INSERT INTO DATA values('CustA', 4, 2);
INSERT INTO DATA values('CustA', 9, 3);
INSERT INTO DATA values('CustB', 8, 1);
INSERT INTO DATA values('CustB', 3, 2);
INSERT INTO DATA values('CustB', 1, 3);
INSERT INTO DATA values('CustB', 1, 3);
INSERT INTO DATA values('CustC', 2, 1);
INSERT INTO DATA values('CustC', 2, 1);
INSERT INTO DATA values('CustC', 7, 2);
INSERT INTO DATA values('CustC', 1, 3);

what kind of select can i do to get:

Day   CustA  CustB CustC
1       5     8      4
2       4     3      7
3       9     2      1


--
[ Jim Mercer        jim@reptiles.org         +1 416 410-5633 ]
[          I want to live forever, or die trying.            ]

Bonjour Jim,

Le jeudi 1 août 2002 à 21:07:32, vous écriviez :

JM> what kind of select can i do to get:

JM> Day   CustA  CustB CustC
JM> 1       5     8      4
JM> 2       4     3      7
JM> 3       9     2      1

This one :
SELECT day,
        SUM(CASE WHEN customer='CustA' THEN widgets ELSE 0 END) AS "CustA",
        SUM(CASE WHEN customer='CustB' THEN widgets ELSE 0 END) AS "CustB",
        SUM(CASE WHEN customer='CustC' THEN widgets ELSE 0 END) AS "CustC",
        SUM(1) as Total
FROM DATA
GROUP BY day
See : http://php.weblogs.com/ADOdb_manual#pivot

--
Cordialement,
 Daniel                            mailto:pgsql@ajornet.com