我有一个像SO这样的问答网站。我还有一个表格,其中包含问题和答案及其编辑版本。这是我的表结构:
// QandA
+----+---------+---------------------------+---------+------+-----------+
| id | title | body | related | type | edited_id |
+----+---------+---------------------------+---------+------+-----------+
| 1 | title1 | question content | NULL | 0 | NULL |
| 2 | | answer content | 1 | 1 | NULL |
| 3 | title2 | question content | NULL | 0 | NULL |
| 4 | | answer content | 3 | 1 | NULL |
| 5 | | answer content | 1 | 1 | NULL |
| 6 | | answer content (edited) | NULL | 1 | 2 |
| 7 | title3 | question content | NULL | 0 | NULL |
| 8 | title1 | question content (edited) | NULL | 0 | 1 |
| 9 | | answer content | 7 | 1 | NULL |
| 10 | title1 | question content (edited) | NULL | 0 | 1 |
| 11 | title3 | question content (edited) | NULL | 0 | 7 |
+----+---------+---------------------------+---------+------+-----------+
栏目说明:
related
column:
-
NULL
对于问题和问题/答案的编辑版本
-
{the id of its own question}
寻求答案
type
column:
edited_id
column: (原帖id)
-
NULL
意味着这是一个原始问题/答案
-
{any number}
意味着它是问题/答案的编辑版本。
现在我需要一个查询来选择一个问题及其所有答案。注意到我需要选择the last它们的编辑版本(如果它们已被编辑).
示例1:我有这个值::id = 1
我想要这个输出:
+----+---------+---------------------------+---------+------+-----------+
| id | title | body | related | type | edited_id |
+----+---------+---------------------------+---------+------+-----------+
| 10 | title1 | question content (edited) | NULL | 0 | 1 |
| 6 | | answer content (edited) | NULL | 1 | 2 |
| 5 | | answer content | 1 | 1 | NULL |
+----+---------+---------------------------+---------+------+-----------+
示例2:我有这个值::id = 3
我想要这个输出:
+----+---------+---------------------------+---------+------+-----------+
| id | title | body | related | type | edited_id |
+----+---------+---------------------------+---------+------+-----------+
| 3 | title2 | question content | NULL | 0 | NULL |
| 4 | | answer content | 3 | 1 | NULL |
+----+---------+---------------------------+---------+------+-----------+
示例2:我有这个值::id = 7
我想要这个输出:
// QandA
+----+---------+---------------------------+---------+------+-----------+
| id | title | body | related | type | edited_id |
+----+---------+---------------------------+---------+------+-----------+
| 11 | title3 | question content (edited) | NULL | 0 | 7 |
| 9 | | answer content | 7 | 1 | NULL |
+----+---------+---------------------------+---------+------+-----------+
这是我当前的查询:
SELECT *
FROM QandA
WHERE (id = :id AND type = 0) OR
(related = :id AND type = 1)
ORDER BY type -- noted that the order of answers doesn't matter
如您所见,我的查询不支持编辑版本。无论如何,当该帖子有已编辑的行时,如何替换已编辑的帖子版本?
Note:请不要告诉我“不要将问题和答案放在同一个表中”,因为我知道。但现在我需要解决上面的问题。