UNION很多表，并且还包含空结果

Question

似乎这个问题有很多“接近答案”，但没有一个完全符合我的问题。

SELECT 
 'table1' AS table,
  table1.id, 
  pivot1.field1, 
  pivot2.field2, 
  pivot3.field3
FROM table1
LEFT JOIN pivot1 ON (...)
LEFT JOIN pivot2 ON (...)
LEFT JOIN pivot3 ON (...)
WHERE (...)

UNION ALL

SELECT 
 'table2' AS table,
  table2.id, 
  pivot1.field1, 
  pivot2.field2, 
  pivot3.field3
FROM table2
LEFT JOIN pivot1 ON (...)
LEFT JOIN pivot2 ON (...)
LEFT JOIN pivot3 ON (...)
WHERE (...)

UNION ALL

SELECT 
 'table3' AS table,
  table3.id, 
  pivot1.field1, 
  pivot2.field2, 
  pivot3.field3
FROM table2
LEFT JOIN pivot1 ON (...)
LEFT JOIN pivot2 ON (...)
LEFT JOIN pivot3 ON (...)
WHERE (...)

ORDER BY (...)

这很好地仅从所有表中获取匹配结果。

示例

table1|1|val|val|val
table1|2|val|val|val
table1|3|val|val|val
table2|1|val|val|val

SQLFiddle

但是，我还要为表格添加一行，但没有结果。

如果我尝试这样添加一个计数列，我发现每个表的结果都被分组：

SELECT 
  COUNT(table1.id) AS matches,
 'table1' AS table,
  table1.id, 
  pivot1.field1, 
  pivot2.field2, 
  pivot3.field3
FROM table1
LEFT JOIN pivot1 ON (...)
LEFT JOIN pivot2 ON (...)
LEFT JOIN pivot3 ON (...)
WHERE (...)

UNION ALL

SELECT 
  COUNT(table2.id) AS matches,
 'table2' AS table,
  table2.id, 
  pivot1.field1, 
  pivot2.field2, 
  pivot3.field3
FROM table2
LEFT JOIN pivot1 ON (...)
LEFT JOIN pivot2 ON (...)
LEFT JOIN pivot3 ON (...)
WHERE (...)

UNION ALL

SELECT 
  COUNT(table3.id) AS matches,
 'table3' AS table,
  table3.id, 
  pivot1.field1, 
  pivot2.field2, 
  pivot3.field3
FROM table2
LEFT JOIN pivot1 ON (...)
LEFT JOIN pivot2 ON (...)
LEFT JOIN pivot3 ON (...)
WHERE (...)

ORDER BY (...)

示例

3|table1|1   |val |val |val
1|table2|1   |val |val |val
0|table3|NULL|NULL|NULL|NULL

SQLFiddle

您如何建议我同时获得两个结果，如下所示：

3|table1|1   |val |val |val
3|table1|2   |val |val |val
3|table1|3   |val |val |val
1|table2|1   |val |val |val
0|table3|NULL|NULL|NULL|NULL

编辑：一些人要求使用实际的SQL，以便他们可以处理查询，因此为了方便起见，我插入了一些SQLFiddle。感谢所有尝试提供帮助的人。

SIMPLIFIED：除了SQLFiddle，还有一些人要求简化的示例，所以这是给他们的：

table1     table2     table3
id|a|b|c   id|a|b|c   id|a|b|c
1 |1|0|0   1 |0|2|0   1 |3|3|0
2 |1|1|1   2 |2|0|0   2 |0|3|0
3 |1|1|0   3 |2|0|2   3 |3|0|0

SELECT COUNT(*) AS n, '1' AS t, id,a,b,c FROM table1 WHERE a=1
UNION ALL
SELECT COUNT(*) AS n, '2' AS t, id,a,b,c FROM table2 WHERE b=2
UNION ALL
SELECT COUNT(*) AS n, '3' AS t, id,a,b,c FROM table3 WHERE c=3

此示例忽略了联接和排序，以简化它。结果，我们想要的是以下内容：

 n| t|  id|   a|   b|   c
-------------------------
 3| 1|   1|   1|   0|   0
 3| 1|   2|   1|   1|   1
 3| 1|   3|   1|   1|   0
 1| 2|   1|   0|   2|   0
 0| 3|NULL|NULL|NULL|NULL

但是尝试添加/删除“ COUNT（*）AS n”查询片段以查看结果如何变化。

Answer 1

SELECT 
  COUNT(table1.id) AS matches,
 'table1' AS table,
  table1.id, 
  pivot1.field1, 
  pivot2.field2, 
  pivot3.field3
FROM table1
LEFT JOIN pivot1 ON (...)
LEFT JOIN pivot2 ON (...)
LEFT JOIN pivot3 ON (...)
WHERE (...)

UNION ALL

SELECT 
  0 AS matches,
 'table1' AS table,
  null, 
  null, 
  null, 
  null
WHERE NOT EXISTS (
    SELECT *
    FROM table1
    WHERE (...). -- same where clause as above
)