Question

我已将用户帖子存储在名为posts with fields

的表中

id
userid
posttitle
status

我已在fav_posts表格中存储了用户收藏的帖子，其中包含字段

id
post_id
userid

发布表

代码：

id    userid     posttitle status
1   1200    title 1 Active 
2   1200    title 2 Active 
3   1200    title 3 Active 
4   1200    title 4 Active 
5   1201    title 5 Active 
6   1201    title 6 Active 
7   1201    title 7 Active 
8   1201    title 8 Active

Fav_posts表代码：

id  post_id     userid
1   1   1200
2   2   1201
3   5   1202
4   6   1202
5   6   1201
6   8   1201
7   8   1200
8   7   1200

现在如果我输入一个用户我必须得到两个表中都存在的记录但应该只来一次并具有单独的Field值即如果我输入id为1200 结果应该是

代码：

post_id     title   post_came_in
1   title 1 BOTH
8   title 8 FAV
7   title 7 FAV
2   title 2 MYPOST
3   title 3 MYPOST
4   title 4 MYPOST

我能够列出工会名单但我不知道如何在检查后在结果集中包含第三个字段，并发现同一记录包含在我的帖子和收藏的帖子中

我使用以下查询来获取联盟结果

SELECT post_id,title 
FROM posts 
LEFT JOIN fav_posts ON posts.id = fav_posts.post_id WHERE fav_posts.userid = 1200
UNION ALL
SELECT id AS post_id,title FROM posts WHERE userid = 1200

请告诉我如何在查询中包含检查标准

此致 ANEES

Answer 1

SELECT 
 post_id, title,
 CASE WHEN posts.id IS NULL THEN 'FAV'
      WHEN fav_posts.id IS NULL AND posts.id IS NOT NULL THEN 'MYPOST'
      ELSE 'BOTH'
 END post_came_in
FROM 
 posts FULL JOIN fav_posts ON posts.id = fav_posts.post_id 
WHERE 
 (fav_posts.userid = 1200) OR (posts.userid = 1200)

Answer 2

SELECT post_id, title, 'FAV' AS `post_came_in` FROM posts LEFT JOIN fav_posts ON posts.id = fav_posts.post_id WHERE fav_posts.userid = 1200
UNION ALL
SELECT id AS post_id, title, 'MYPOST' AS `post_came_in` FROM posts WHERE userid = 1200

在Union Query中添加带条件的额外列

2 个答案: