如何在MySQL中创建View以将第二个表中的行组合为第一个

Question

我需要在MySQL中创建VIEW，它可以组合两个表，对于第一个表中的每一行，必须添加第二个表中的列，但因为行数据必须格式化为多个fild，每个单元都有多个CSV行。

我最初的方法是使用MySQL VIEW，但是我无法找到将第二个表中的多个行数据显示为视图表中的CSV单个单元格数据的方法。

以下是一些例子：

1st table: gears
+------------+------------------------+-----------------+
| MainGearID | MainGearName           | MainGearType    |
+------------+------------------------+-----------------+
|          1 | Main Drive             | Spur            |
|          2 | Secondary Drive        | Spur            |
|          3 | Backup Secondary Drive | Hypoid          |
|          4 | AUX Drive              | Rack and pinion |
+------------+------------------------+-----------------+

2nd table: orbitinggears:
+----------+------------+--------------+--------------+
| OrbitaID | MainGearID | OrbitalType  | OrbitalValue |
+----------+------------+--------------+--------------+
|        1 |          1 | Spur         | 112          |
|        2 |          1 | Spur         | 280          |
|        3 |          2 | Spur         | 144          |
|        4 |          2 | Spur         | 248          |
|        5 |          3 | Helical      | 18           |
|        6 |          4 | Spur         | 144          |
+----------+------------+--------------+--------------+

Required View:
+------------+------------------------+-----------------+----------+---------+
| MainGearID | MainGearName           | MainGearType    | Spur     | Helical |
+------------+------------------------+-----------------+----------+---------+
|          1 | Main Drive             | Spur            | 112,280, |         |
|          2 | Secondary Drive        | Spur            | 144,248, |         |
|          3 | Backup Secondary Drive | Hypoid          |          | 18,     |
|          4 | AUX Drive              | Rack and pinion | 144,     |         |
+------------+------------------------+-----------------+----------+---------+

有人知道如何以这种方式创建视图吗？

Answer 1

您可以将GROUP_CONCAT与IF()：

一起使用

CREATE VIEW v6 AS 
SELECT a.MainGearID, a.MainGearName, a.MainGearType, 
   GROUP_CONCAT(IF(b.OrbitalType='Spur',b.OrbitalValue,null)) AS Spur,
   GROUP_CONCAT(IF(b.OrbitalType='Helical',b.OrbitalValue,null)) AS Helical
 FROM gears a
 JOIN orbitinggears b on b.MainGearID=a.MainGearID
 GROUP BY a.MainGearID;