在这种情况下什么是合适的查询

Question

Here is my scenario :

A user can post something on his profile, he can also share another user's post. I want to select in a query every post and share he has done (ordered using datetime). I just can't find the appropriate query with my basic MySQL skills. Help me find my way threw this! Cheers.

Table post

id   user_id     content        datetime
1    100         Loremipsum1    2013-03-04 19:35:02 
2    200         Loremipsum2    2013-03-03 19:30:02 
3    200         Loremipsum3    2013-03-01 19:25:02

Table share

id    user_id     target_id     post_id    datetime
1     100         200           2          2013-02-01 19:25:02
2     100         200           3          2013-02-01 19:24:02
3     200         100           1          2013-01-01 19:25:02

Let's say I would like to get every result for my user 100, the desired result would be

id   user_id     content        datetime
1    100         Loremipsum1    2013-03-04 19:35:02 
2    200         Loremipsum2    2013-03-03 19:30:02 
3    200         Loremipsum3    2013-03-01 19:25:02

because user 100 shared both post of user 200.

EDIT : Some people think that I'm trying to be lazy and to have someone else doing my work for me. So here is where I am at the moment in my query.

SELECT *
FROM user_stream
LEFT JOIN user_share
ON user_stream.user_id = user_share.user_id
WHERE user_id = 100

My problem here is that I need to select the content from my target_id not my user_id. But I have no idea of the target_id value. It could also be multiple value (if a user share multiple post).

Answer 1

Not completely sure I understand what you're looking for, but to get a list of posts that a user has either created or shared, you can use UNION to combine the results. Something like this:

SELECT *
FROM (
    SELECT id, user_id, datetime, 'P' as type
    FROM post
    UNION 
    SELECT post_id, user_id, datetime, 'S' as type
    FROM share
) t
WHERE user_id = 100
ORDER BY datetime 

The type tells you whether it were a post or a share.

---

Edit: Given your comments, then it looks like you just want the posts. Try this:

SELECT *
FROM post
WHERE id IN (
    SELECT id
    FROM post
    WHERE user_id = 100
    UNION 
    SELECT post_id
    FROM share
    WHERE user_id = 100
)
ORDER BY datetime