如何在 mysql 中创建成对枢轴 table 的矩阵

Question

我有这样的数据：

id_jarak    idkota1 idkota2 jarak
1           1       2       1
2           1       3       2
3           1       4       3
4           2       1       1
5           2       3       5
8           3       5       8
7           3       2       5
6           3       1       2
9           4       1       3
10          4       5       9
11          5       3       8
12          5       4       9

并且我尝试从该数据中创建主元和矩阵这是我的查询

SELECT a.idkota1,
( IF(a.idkota2 = '1' or b.idkota1 = '1', a.jarak, 0 ) ) AS 1s,
( IF(a.idkota2 = '2' or b.idkota1 = '2', a.jarak, 0 ) ) AS 2s,
( IF(a.idkota2 = '3' or b.idkota1 = '3', a.jarak, 0 ) ) AS 3s,
( IF(a.idkota2 = '4' or b.idkota1 = '4', a.jarak, 0 ) ) AS 4s,
( IF(a.idkota2 = '5' or b.idkota1 = '5', a.jarak, 0 ) ) AS 5s

FROM ms_jarak_kota as a
inner join ms_jarak_kota as b
on a.idkota1>=b.idkota2
GROUP BY b.idkota2

但是结果是这样的

idkota1 1s  2s  3s  4s  5s
1       0   1   0   0   0
2       1   0   0   0   0
3       2   0   0   0   0
4       3   0   0   0   0
5       0   0   8   0   0

我的期望结果是这样的

    1s  2s  3s  4s  5s
  1 0   1   2   3   
  2 1   0   5       
  3 2   5   0       8
  4 3           0   9
  5         8   9   0

我的查询有问题，如何解决？谢谢

Answer 1

试试这个方法：

SELECT idkota1, 
       MAX(CASE WHEN idkota2 = 1 THEN jarak END) AS '1s',
       MAX(CASE WHEN idkota2 = 2 THEN jarak END) AS '2s',
       MAX(CASE WHEN idkota2 = 3 THEN jarak END) AS '3s',
       MAX(CASE WHEN idkota2 = 4 THEN jarak END) AS '4s',
       MAX(CASE WHEN idkota2 = 5 THEN jarak END) AS '5s'
FROM ms_jarak_kota
GROUP BY idkota1

Demo here

如何在 mysql 中创建成对枢轴 table 的矩阵

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