MYSQL查询-在Where子句中使用Select语句

Question

Objective: Get all videos that match tags a user has liked (teams and players)...

I have four tables.

I need to get get all of a user's players from the user_player_tracker table

I need to get get all of a user's teams from the user_team_tracker table

I need to find all tags where a user's players or a user's teams exist from the user_video_tags table

I need to ultimately get the id and video_url where the user_video_tags video_id are the id from user_videos

I can't wrap my head around how to do this all, here is what I have so far...

SELECT v.id, v.video_url FROM user_videos v
LEFT JOIN user_video_tags t
ON t.video_id = v.id
WHERE (
    SELECT t.video_id FROM user_video_tags t
    LEFT JOIN user_player_tracker up 
    ON up.site_id = t.site_id AND up.player_id = t.player_id
    WHERE up.user_id = {$userid} )
|| (
    SELECT t.video_id FROM user_video_tags t
    LEFT JOIN user_team_tracker ut 
    ON ut.site_id = t.site_id AND ut.team_id = t.player_id
    WHERE ut.user_id = {$userid} ) 

Answer 1

The answer was that I had to do this in two steps. First, get all the tagged videos using a Union. I used 'group by' to not get any duplicates in each query, and the 'union' instead of 'union all' got me all unique video_id's from the combined results. I ordered the list of videos using php arsort($results) because I couldn't figure out how to order using group by and union in the mysql statement. After that I just had to loop through each result to get the video for each tag.

    $results = $wpdb->get_results("
    SELECT t.video_id FROM user_video_tags t
    LEFT JOIN user_player_tracker up 
    ON up.site_id = t.site_id AND up.player_id = t.player_id
    WHERE up.user_id = {$userid}
    GROUP BY t.video_id
    UNION
    SELECT t.video_id FROM user_video_tags t
    LEFT JOIN user_team_tracker up 
    ON up.site_id = t.site_id AND up.team_id = t.team_id
    WHERE up.user_id = {$userid}
    GROUP BY t.video_id
    LIMIT 20");

    arsort($results);

if($results){
    foreach ($results as $item) {
        // call another function that gets the video
        $html .= get_media($item->video_id);
    }
} else {
    $html .= 'No videos found for this user, wEird.<br/>';
}