mariadb complex 基于公共列组合表列，并在输出的公共列中找不到时添加新列

Question

我有 3 个如下表。其中 id, fcd, ref 列在表中是通用的，我正在尝试将所有表列合并到单个表中。

MariaDB [test]> select * from t1;
+----+-----+-----+------+------+
| id | fcd | ref | c1   | c2   |
+----+-----+-----+------+------+
|  1 |   1 | 1.0 | 0.10 | 2.00 |
|  1 |   2 | 1.5 | 0.40 | 2.22 |
|  3 |   1 | 2.0 | 0.10 | 4.30 |
|  3 |   2 | 3.2 | 0.01 | 6.60 |
|  5 |   3 | 7.5 | 0.00 | 7.70 |
+----+-----+-----+------+------+
5 rows in set (0.001 sec)

MariaDB [test]> select * from t2;
+----+-----+------+------+------+
| id | fcd | ref  | c3   | c4   |
+----+-----+------+------+------+
|  1 |   1 | 1.00 | 0.06 | 0.76 |
|  1 |   2 | 1.20 | 0.32 | 0.87 |
|  5 |   2 | 6.50 | 0.44 | 0.09 |
|  5 |   3 | 6.68 | 0.47 | 0.08 |
+----+-----+------+------+------+
4 rows in set (0.001 sec)

MariaDB [test]> select * from t3;
+----+-----+-----+------+------+
| id | fcd | ref | c5   | c6   |
+----+-----+-----+------+------+
|  1 |   3 | 1.1 | 0.02 | 0.12 |
|  1 |   4 | 2.0 | 0.23 | 0.11 |
|  7 |   1 | 3.2 | 0.45 | 0.43 |
|  7 |   2 | 7.5 | 0.54 | 0.67 |
+----+-----+-----+------+------+
4 rows in set (0.000 sec)

这是我尝试使用联合没有运气

MariaDB [test]> select id,fcd,ref,c1,c2,null c3, null c4, null c5, null c6 from t1  union all  select id,fcd,ref,null c1, null c2, c3, c4,null c5, null c6 from t2 union all select id,fcd,ref,null c1, null c2, null c3, null c4,c5, c6 from t3 order by id, fcd, ref;
+----+-----+------+------+------+------+------+------+------+
| id | fcd | ref  | c1   | c2   | c3   | c4   | c5   | c6   |
+----+-----+------+------+------+------+------+------+------+
|  1 |   1 | 1.00 | NULL | NULL | 0.06 | 0.76 | NULL | NULL |
|  1 |   1 | 1.00 | 0.10 | 2.00 | NULL | NULL | NULL | NULL |
|  1 |   2 | 1.20 | NULL | NULL | 0.32 | 0.87 | NULL | NULL |
|  1 |   2 | 1.50 | 0.40 | 2.22 | NULL | NULL | NULL | NULL |
|  1 |   3 | 1.10 | NULL | NULL | NULL | NULL | 0.02 | 0.12 |
|  1 |   4 | 2.00 | NULL | NULL | NULL | NULL | 0.23 | 0.11 |
|  3 |   1 | 2.00 | 0.10 | 4.30 | NULL | NULL | NULL | NULL |
|  3 |   2 | 3.20 | 0.01 | 6.60 | NULL | NULL | NULL | NULL |
|  5 |   2 | 6.50 | NULL | NULL | 0.44 | 0.09 | NULL | NULL |
|  5 |   3 | 6.68 | NULL | NULL | 0.47 | 0.08 | NULL | NULL |
|  5 |   3 | 7.50 | 0.00 | 7.70 | NULL | NULL | NULL | NULL |
|  7 |   1 | 3.20 | NULL | NULL | NULL | NULL | 0.45 | 0.43 |
|  7 |   2 | 7.50 | NULL | NULL | NULL | NULL | 0.54 | 0.67 |
+----+-----+------+------+------+------+------+------+------+
13 rows in set (0.001 sec)

如您所见1 | 1 | 1 存在重复，以上一个没有正确组合

这是我所期望的

| id    | fcd   | ref   | c1    | c2    | c3    | c4    | c5    | c6    |
|----   |-----  |------ |------ |------ |------ |------ |------ |------ |
| 1     | 1     | 1     | 0.1   | 2     | 0.06  | 0.76  | NULL  | NULL  |
| 1     | 2     | 1.2   | NULL  | NULL  | 0.32  | 0.87  | NULL  | NULL  |
| 1     | 2     | 1.5   | 0.4   | 2.22  | NULL  | NULL  | NULL  | NULL  |
| 1     | 3     | 1.1   | NULL  | NULL  | NULL  | NULL  | 0.02  | 0.12  |
| 1     | 4     | 2     | NULL  | NULL  | NULL  | NULL  | 0.23  | 0.11  |
| 3     | 1     | 2     | 0.1   | 4.3   | NULL  | NULL  | NULL  | NULL  |
| 3     | 2     | 3.2   | 0.01  | 6.6   | NULL  | NULL  | NULL  | NULL  |
| 5     | 2     | 6.5   | NULL  | NULL  | 0.44  | 0.09  | NULL  | NULL  |
| 5     | 3     | 6.68  | NULL  | NULL  | 0.47  | 0.08  | NULL  | NULL  |
| 5     | 3     | 7.5   | 0     | 7.7   | NULL  | NULL  | NULL  | NULL  |
| 7     | 1     | 3.2   | NULL  | NULL  | NULL  | NULL  | 0.45  | 0.43  |
| 7     | 2     | 7.5   | NULL  | NULL  | NULL  | NULL  | 0.54  | 0.67  |

请高人帮帮我，不知道怎么解决

Answer 1

您可以group by id,fcd,ref对您的查询结果进行汇总：

select id,fcd,ref,max(c1) c1,max(c2) c2,max(c3) c3,max(c4) c4,max(c5) c5,max(c6) c6 
from (  
  select id,fcd,ref,c1,c2,null c3, null c4, null c5, null c6 from t1  
  union all  
  select id,fcd,ref,null c1, null c2, c3, c4,null c5, null c6 from t2 
  union all 
  select id,fcd,ref,null c1, null c2, null c3, null c4,c5, c6 from t3 
) t
group by id,fcd,ref
order by id,fcd,ref;

请参阅demo。

Answer 2

通过在 id、fcd、ref 列上使用 UNION 而不是 UNION ALL，您可以获得相同的结果：

SELECT t.id,
       t.fcd,
       t.ref,
       t1.c1,
       t1.c2,
       t2.c3,
       t2.c4,
       t3.c5,
       t3.c6
FROM
  (SELECT id,
          fcd,
          ref
   FROM t1
   UNION SELECT id,
                fcd,
                ref
   FROM t2
   UNION SELECT id,
                fcd,
                ref
   FROM t3) AS t
LEFT JOIN t1 USING(id,
                   fcd,
                   ref)
LEFT JOIN t2 USING(id,
                   fcd,
                   ref)
LEFT JOIN t3 USING(id,
                   fcd,
                   ref)
ORDER BY id,
         fcd,
         ref;

ref:fiddle（感谢@forpas 提供基础数据）