mysql行列转换

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本文介绍了一种使用MySQL进行复杂数据汇总的方法，通过多种查询技巧如WITH ROLLUP、UNION及动态SQL等实现灵活的数据透视表效果。

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数据样本：
create table tx(
id int primary key,
c1 char(2),
c2 char(2),
c3 int
);
insert into tx 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);

mysql> select * from tx;
+----+------+------+------+
| id | c1 | c2 | c3 |
+----+------+------+------+
| 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 |
+----+------+------+------+
20 rows in set (0.00 sec)
mysql>
期望结果
+------+-----+-----+-----+-----+------+
|C1 |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 |
+------+-----+-----+-----+-----+------+
1. 利用SUM(IF()) 生成列 + WITH ROLLUP 生成汇总行,并利用 IFNULL将汇总行标题显示为 Total
mysql>
SELECT
IFNULL(c1,'total') AS total,
SUM(IF(c2='B1',c3,0)) AS B1,
SUM(IF(c2='B2',c3,0)) AS B2,
SUM(IF(c2='B3',c3,0)) AS B3,
SUM(IF(c2='B4',c3,0)) AS B4,
SUM(IF(c2='total',c3,0)) AS total
FROM (
SELECT c1,IFNULL(c2,'total') AS c2,SUM(c3) AS c3
FROM tx GROUP BY c1,c2
WITH ROLLUP
HAVING c1 IS NOT NULL
) AS A
GROUP BY c1
WITH ROLLUP;

+-------+------+------+------+------+-------+
| total | 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 |
+-------+------+------+------+------+-------+
5 rows in set, 1 warning (0.00 sec)
2. 利用SUM(IF()) 生成列 + UNION 生成汇总行,并利用 IFNULL将汇总行标题显示为 Total
mysql>
select c1,
sum(if(c2='B1',C3,0)) AS B1,
sum(if(c2='B2',C3,0)) AS B2,
sum(if(c2='B3',C3,0)) AS B3,
sum(if(c2='B4',C3,0)) AS B4,SUM(C3) AS TOTAL
from tx
group by C1
UNION
SELECT 'TOTAL',sum(if(c2='B1',C3,0)) AS B1,
sum(if(c2='B2',C3,0)) AS B2,
sum(if(c2='B3',C3,0)) AS B3,
sum(if(c2='B4',C3,0)) AS B4,SUM(C3) FROM TX;

+-------+------+------+------+------+-------+
| c1 | 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 |
+-------+------+------+------+------+-------+
5 rows in set (0.00 sec)
mysql>

3. 利用SUM(IF()) 生成列,直接生成结果不再利用子查询
mysql>
select
ifnull(c1,'total'),
sum(if(c2='B1',C3,0)) AS B1,
sum(if(c2='B2',C3,0)) AS B2,
sum(if(c2='B3',C3,0)) AS B3,
sum(if(c2='B4',C3,0)) AS B4,SUM(C3) AS TOTAL
from tx
group by C1 with rollup ;

+--------------------+------+------+------+------+-------+
| ifnull(c1,'total') | 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 |
+--------------------+------+------+------+------+-------+
5 rows in set (0.00 sec)
mysql>

4. 动态，适用于列不确定情况，
mysql> SET @EE='';
mysql> SELECT @EE:=CONCAT(@EE,'SUM(IF(C2=\'',C2,'\'',',C3,0)) AS ',C2,',') FROM (SELECT DISTINCT C2 FROM TX) A;

mysql> SET @QQ=CONCAT('SELECT ifnull(c1,\'total\'),',LEFT(@EE,LENGTH(@EE)-1),' ,SUM(C3) AS TOTAL FROM TX GROUP BY C1 WITH ROLLUP');
Query OK, 0 rows affected (0.00 sec)

mysql> PREPARE stmt2 FROM @QQ;
Query OK, 0 rows affected (0.00 sec)
Statement prepared
mysql> EXECUTE stmt2;
+--------------------+------+------+------+------+-------+
| ifnull(c1,'total') | 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 |
+--------------------+------+------+------+------+-------+
5 rows in set (0.00 sec)
mysql>
其实数据库中也可以用 CASE WHEN / DECODE 代替 IF

sum(if(c2='B1',C3,0)) AS B1
可改写为
sum(case c2 when 'B1' then C3 else 0 end) AS B1

原文地址：http://blog.chinaunix.net/u3/90603/showart_2017912.html