valueconverter - 如何将单行转换为一列？

Question

如何将一行的列转换为一行？

表中数据如下：

+------+------+------+------+
| col1 | col2 | col3 | col4 |
+------+------+------+------+
|  a1  |  a2  |  a3  |  a4  |
+------+------+------+------+

所需的输出：该行中的所有值都应该放在如下的单列中。

+---------------+
|   All_cols    |
+---------------+
|  a1,a2,a3,a4  |
+---------------+

如图所示：这里mytable总是有一个记录，所以我需要如下输出。

想要避免低于 sql，因为它需要多个连接：

select a1.name from  accounts a1 where a1.id='658f3b73-8260-5a7a-ae7e-54c25deded36'

union

Select a2.name from accounts a1
left join accounts a2 on a1.id=a2.parent_id where a1.id='658f3b73-8260-5a7a-ae7e-54c25deded36'

union

Select a3.name from accounts a1
left join accounts a2 on a1.id=a2.parent_id
left join accounts a3 on a2.id=a3.parent_id where a1.id='658f3b73-8260-5a7a-ae7e-54c25deded36'

union

Select a4.name from accounts a1
left join accounts a2 on a1.id=a2.parent_id
left join accounts a3 on a2.id=a3.parent_id
left join accounts a4 on a3.id=a4.parent_id where a1.id='658f3b73-8260-5a7a-ae7e-54c25deded36'

union

Select a5.name from accounts a1
left join accounts a2 on a1.id=a2.parent_id
left join accounts a3 on a2.id=a3.parent_id
left join accounts a4 on a3.id=a4.parent_id
left join accounts a5 on a4.id=a5.parent_id where a1.id='658f3b73-8260-5a7a-ae7e-54c25deded36'

Answer 1

你可以打UNION四个电话

SELECT col1 FROM mytable
UNION
SELECT col2 FROM mytable
UNION
SELECT col3 FROM mytable
UNION
SELECT col4 FROM mytable

将输出

你这么说

mytable 总是有一个记录。

请注意，如果您有多个记录，明智的做法是在上面的每个语句中使用相同的WHERE条件。SELECT