mysql行列转换方法总结

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