mysql行列转换方法总结

这是一道行转列并且构造交叉表的问题：

http://topic.csdn.net/u/20090530/23/0b782674-4b0b-4cf5-bc1a-e8914aaee5ab.html

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

+------+-----+-----+-----+-----+------+
|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 |
+------+-----+-----+-----+-----+------+

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