php - 为每个帖子选择反对票和赞成票 php mysql

Question

我有一个论坛，用户可以在其中发布问题并可以投赞成票和投反对票。

我想获得每个帖子的 upvote 和 downvote。

我之前所做的是在 3 组查询中执行此操作。

$data = mysqli_query($con,"select * from posts");
while($row = mysqli_fetch_assoc($data)){
  $pid  = $row['post_id'];
  $up = mysqli_fetch_assoc(mysqli_query("SELECT COUNT(*) as c FROM up WHERE post_id = $pid"))['c'];
  $down = mysqli_fetch_assoc(mysqli_query("SELECT COUNT(*) as c FROM down WHERE post_id = $pid"))['c'];
}

谁能告诉我如何在一个查询中做这些事情，因为如果在第一个查询中得到很多帖子，那么会有很多查询做。

Answer 1

您可以使用子查询并将所有内容放在第一个查询中。

这可能是一个好的开始:

$data = mysqli_query($con, "select posts.*, " . 
                           "(SELECT COUNT(*) FROM up WHERE post_id = posts.post_id) as totalUp, " . 
                           "(SELECT COUNT(*) FROM down WHERE post_id = posts.post_id) as totalDown " .
                           "from posts");
while($row = mysqli_fetch_assoc($data)){
  // ...
}