從Xoops數據庫中計數並插入評論

Question

我試圖將Xoops帖子轉換爲Wordpress。作爲其中的一部分，我想獲得一個主題的評論數。帖子和回覆在相同的「topic_id」上。如何計算它們並將其發佈到新列？

從這裏DB當前狀態

topic_id | subject    |comment_count| 
+________+_____________________+_____________+ 
1 | welcome    | 
1 | Re: welcome   | 
2 | hello world   | 
2 | Re: hello world  | 
2 | Re: hello world  | 
3 | hello friends  | 

我想借此（topic_id計數 - 1）重播的號碼（評論數）。引導我在MYSQL中查詢

我想將輸出放在同一個表中。 （COMMENT_COUNT）

DB預期輸出

| topic_id | subject    |comment_count| 
    +________+_____________________+_____________+ 
    | 1 | welcome    | 1 
    | 1 | Re: welcome   | 1 
    | 2 | hello world   | 2 
    | 2 | Re: hello world  | 2 
    | 2 | Re: hello world  | 2 
    | 3 | hello friends  | 0 

Answer 1

select *,t2.comment_count from table t1 
    join 
    (
     select count(*),CONCAT('Re', ' ', subject) 
     as replay,topic_id as comment_count 
     from table 
     where suject=replay group by topic_id 
    ) as t2 on t1.topic_id=t2.topic_id 

Answer 2

SELECT 
    xoops.topic_id, topic, xoops2.commentCount 
FROM 
    xoops JOIN 
(
    SELECT 
     xoops.topic_id, 
     commentCount = COUNT(1) - 1 
    FROM 
     xoops 
    GROUP BY 
     xoops.topic_id 
     ) AS xoops2 ON xoops.topic_ID = xoops2.topic_ID