MySQL选择查询内部连接表，其中2个正则表达式针对不同的表

Question

Im using PHP MySQLi prepared statements for the querying

$stmt = $dbconnect->prepare("

    SELECT COUNT(r.review_id)
         , p.postid
         , p.title
         , p.tags
         , p.ltags
         , p.status
         , p.timestamp 
      FROM njdb.post_review r
      JOIN njdb.post_si p
     WHERE r.postid REGEXP ? 
       AND r.review_status = 'a' 
       AND p.postid REGEXP ? 
       AND p.status = 'a';

   ");
$stmt->bind_param('ss',$search,$search);
$stmt->execute();
$stmt->bind_result($result_post_review, $result_postid, $result_title, $result_hashtags, $result_location, $result_status, $result_timestamp);

$search is a string with a value like id1|id2|id3|id4

There are 2 tables in play here post_si AND post_review

I am expecting the above to give me the total number of reviews + the details of the post. But I'm having problems in the WHERE area because some of the posts don't have any reviews so the AND post_review.review_status = 'a' is causing some of the problems.

I think what I really need is to use conditional statements but I haven't tried that in mysql if no reviews its ok just get the details of the post and move on to the next post How do I do that? Thanks!

Answer 1

You need to use a LEFT JOIN to get posts that have no matching reviews. You also need a proper join condition, to link posts with their reviews. And a GROUP BY clause to get the counts by post, otherwise you total everything in one result.

SELECT COUNT(r.review_id)
     , p.postid
     , p.title
     , p.tags
     , p.ltags
     , p.status
     , p.timestamp 
  FROM njdb.post_si p
  LEFT JOIN njdb.post_review r ON r.postid = p.postid AND r.review_status = 'a'
 WHERE p.postid REGEXP ? 
   AND p.status = 'a'
 GROUP BY p.postid;