检索评论和有限制的回复

Question

我仍然没有找到正确的方法来按照我想要的方式去做。我试图实现的是评论 post 部分，它将显示 post

的最后 2 个回复

我的表结构是这样的

table post
---------------------
post_id | comment | post_user | post_date

post_reply
---------------------
reply_id | parent_id | reply_user | reply_date

实际上我能够获取所有 post 和所有回复，但我面临的问题是我想限制我获取的 post 的数量和回复的数量我获取的每个 post 并且我还想显示 post 如果没有回复则结果应该如下所示

result
----------------------------------------------
post 1
reply post 1
reply post 1
post 2 
post 3
reply post 3 
reply post 3

当然我想显示这个直到我达到 10 post 并且每个 post 最多附加 2 个回复，当然查询可能更少。实际上我正在为每个 post 的最后一个回复使用一段时间的查询，但每次都使用 11 个查询也许你们知道在更少的查询中做这件事的更好方法

Answer 1

我假设您的 ID 列是 INT 类型。如果不是，您可能必须使用变量来计算每个 post 的回复数，描述为 here.

所以试试这个

SELECT 'POST' AS type, p1.post_id, p1.comment, p1.post_user, p1.post_date, '-' AS reply_id
 FROM post p1
 LIMIT 10

UNION

SELECT 'REPLY' AS type, pr.parent_id AS post_id, 
 '-' AS comment, pr.reply_user AS post_user, pr.reply_date AS post_date, pr.reply_id
 FROM post_reply pr
 JOIN (
     SELECT p2.post_id 
     FROM post p2 
     LIMIT 10
 ) AS tmpPost ON pr.parent_id = tmpPost.post_id
 JOIN (
     SELECT pr.reply_id, COUNT(*) AS row_number
     FROM post_reply pr 
     JOIN post_reply pr2 ON pr.parent_id = pr2.parent_id AND pr.reply_id >= pr2.reply_id
     GROUP BY pr.reply_id
 ) AS tmpPostRN ON tmpPostRN.reply_id = pr.reply_id
 WHERE tmpPostRN.row_number <= 2

ORDER BY post_id ASC, type ASC, reply_id ASC

结果类似于

+-------+---------+-----------+-----------------+------------+----------+
| type  | post_id | comment   | post_user       | post_date  | reply_id |
+-------+---------+-----------+-----------------+------------+----------+
| POST  |       1 | comment1  | user1           | 0000-00-00 | -1       |
| REPLY |       1 | -         | post 1 reply1   | 0000-00-00 | 1        |
| REPLY |       1 | -         | post 1 reply 2  | 0000-00-00 | 2        |
| POST  |       2 | comment2  | user2           | 0000-00-00 | -1       |
| POST  |       3 | comment3  | user3           | 0000-00-00 | -1       |
| REPLY |       3 | -         | post 3 reply 1  | 0000-00-00 | 3        |
| REPLY |       3 | -         | post 3 reply 2  | 0000-00-00 | 4        |
| POST  |       4 | comment4  | user 4          | 0000-00-00 | -1       |
| POST  |       5 | comment5  | user 5          | 0000-00-00 | -1       |
| POST  |       6 | comment6  | user6           | 0000-00-00 | -1       |
| POST  |       7 | comment7  | user7           | 0000-00-00 | -1       |
| POST  |       8 | comment8  | user8           | 0000-00-00 | -1       |
| POST  |       9 | comment9  | user9           | 0000-00-00 | -1       |
| POST  |      10 | comment10 | user10          | 0000-00-00 | -1       |
| REPLY |      10 | -         | post 10 reply 1 | 0000-00-00 | 5        |
| REPLY |      10 | -         | post 10 reply 2 | 0000-00-00 | 6        |
+-------+---------+-----------+-----------------+------------+----------+

您可以在 post_reply table 中插入您的评论栏，而不是第二个查询中的 '-' AS comment（前提是您有评论栏）。您还可以将 reply_id 的 post 设置为您选择的默认值（而不是 -1）。

检索评论和有限制的回复

Retrieving comments and reply with limits

mysql

post

comments

join

limit