mysql 行列动态转换（列联表，交叉表）
（1）动态，适用于列不确定情况
create table table_name(
id int primary key,
col1 char(2),
col2 char(2),
col3 int
);
insert into table_name values
(1 ,'A1','B1',9),
(2 ,'A2','B1',7),
(3 ,'A3','B1',4),
(4 ,'A4','B1',2),
(5 ,'A1','B2',2),
(6 ,'A2','B2',9),
(7 ,'A3','B2',8),
(8 ,'A4','B2',5),
(9 ,'A1','B3',1),
(10 ,'A2','B3',8),
(11 ,'A3','B3',8),
(12 ,'A4','B3',6),
(13 ,'A1','B4',8),
(14 ,'A2','B4',2),
(15 ,'A3','B4',6),
(16 ,'A4','B4',9),
(17 ,'A1','B4',3),
(18 ,'A2','B4',5),
(19 ,'A3','B4',2),
(20 ,'A4','B4',5);
select * from table_name;
+----+------+------+------+
| id | col1 | col2 | col3 |
+----+------+------+------+
| 1 | A1 | B1 | 9 |
| 2 | A2 | B1 | 7 |
| 3 | A3 | B1 | 4 |
| 4 | A4 | B1 | 2 |
| 5 | A1 | B2 | 2 |
| 6 | A2 | B2 | 9 |
| 7 | A3 | B2 | 8 |
| 8 | A4 | B2 | 5 |
| 9 | A1 | B3 | 1 |
| 10 | A2 | B3 | 8 |
| 11 | A3 | B3 | 8 |
| 12 | A4 | B3 | 6 |
| 13 | A1 | B4 | 8 |
| 14 | A2 | B4 | 2 |
| 15 | A3 | B4 | 6 |
| 16 | A4 | B4 | 9 |
| 17 | A1 | B4 | 3 |
| 18 | A2 | B4 | 5 |
| 19 | A3 | B4 | 2 |
| 20 | A4 | B4 | 5 |
+----+------+------+------+
SET @EE='';
SELECT @EE:=CONCAT(@EE,'SUM(IF(col2=\'',col2,'\'',',col3,0)) AS ',col2,',') FROM (SELECT DISTINCT col2 FROM table_name) A;
SET @QQ=CONCAT('SELECT ifnull(col1,\'total\') AS columnA,',LEFT(@EE,LENGTH(@EE)-1),' ,SUM(col3) AS TOTAL FROM table_name GROUP BY col1 WITH ROLLUP');
PREPARE stmt2 FROM @QQ;
EXECUTE stmt2;
+---------+------+------+------+------+-------+
| columnA | B1 | B2 | B3 | B4 | TOTAL |
+---------+------+------+------+------+-------+
| A1 | 9 | 2 | 1 | 11 | 23 |
| A2 | 7 | 9 | 8 | 7 | 31 |
| A3 | 4 | 8 | 8 | 8 | 28 |
| A4 | 2 | 5 | 6 | 14 | 27 |
| total | 22 | 24 | 23 | 40 | 109 |
+---------+------+------+------+------+-------+
（2）第二个字段确定的情况下使用
SELECT
IFNULL(col1,'total') AS total,
SUM(IF(col2='B1',col3,0)) AS B1,
SUM(IF(col2='B2',col3,0)) AS B2,
SUM(IF(col2='B3',col3,0)) AS B3,
SUM(IF(col2='B4',col3,0)) AS B4,
SUM(IF(col2='total',col3,0)) AS total
FROM (
SELECT col1,IFNULL(col2,'total') AS col2,SUM(col3) AS col3
FROM table_name
GROUP BY col1,col2
WITH ROLLUP
HAVING col1 IS NOT NULL
) AS A
GROUP BY col1
WITH ROLLUP;
注： WITH ROLLUP 用于列上求和； SUM(IF(col2='total',col3,0)) AS total 用于行上求和。
（3）第二个字段确定的情况下使用
select ifnull(col1,'total') AS col1,
sum(if(col2='B1',col3,0)) AS B1,
sum(if(col2='B2',col3,0)) AS B2,
sum(if(col2='B3',col3,0)) AS B3,
sum(if(col2='B4',col3,0)) AS B4,SUM(col3) AS TOTAL
from table_name
group by col1 with rollup ;
REF:
http://blog.chinaunix.net/uid-7692530-id-2567582.html
