從多個SELECT子查詢返回多行

Question

詢問

SELECT 
    (SELECT NAME FROM product_component) AS pcNAME,
    (SELECT PROJECT_NAME FROM jira_project) AS jpNAME, 
    (SELECT FILTER_NAME FROM jira_filter) AS jfNAME

每個SELECT都會返回不確定的行數。 我收到錯誤Subquery returns more than 1 row 。 我想要的輸出將是這樣的（快速草圖）：

=======================================
|   pcNAME   |   jpNAME   |  jfNAME   |
=======================================
|    data    |    data    |    data   |
+------------+------------+-----------+
|    data    |    data    |    data   |
+------------+------------+-----------+
|    data    |    data    |    data   |
+------------+------------+-----------+
|            |    data    |    data   |
+------------+------------+-----------+
|            |    data    |    data   |
+------------+------------+-----------+
|            |    data    |           |
+------------+------------+-----------+

每一列可能會產生與其他列不同的行數。 因此，我將要根據最大值生成行數，然后清空其他未填充最大行數的行。

注意：這些表都沒有共享列，因此不能作為INNER JOIN實現

關於如何實現的任何想法？

Answer 1

在MySQL中處理此問題的一種方法，用於變量， union all和聚合：

SELECT MAX(NAME) as NAME, MAX(PROJECT_NAME) as PROJECT_NAME,
       MAX(FILTER_NAME) as FILTER_NAME
FROM ((SELECT (@rnpc := @rnpc + 1) as rn, NAME, NULL as PROJECT_NAME, NULL as FILTER_NAME
      FROM product_component CROSS JOIN
           (SELECT @rnpc := 0) params
      ) UNION ALL
      (SELECT (@rnpn := @rnpn + 1) as rn, NULL, PROJECT_NAME, NULL as FILTER_NAME
      FROM jira_project CROSS JOIN
           (SELECT @rnpn := 0) params
      ) UNION ALL
      (SELECT (@rnf := @rnf + 1) as rn, NAME, NULL as PROJECT_NAME, NULL as FILTER_NAME
      FROM jira_filter CROSS JOIN
           (SELECT @rnf := 0) params
      )
     ) t
GROUP BY rn
ORDER BY rn;