如何从MySQL选择带有子注释的注释？

Question

I have two tables:

'comments'

| id | content | user_id | article_id | parent_id |

'users'

| id | name | photo |

And my queries are:

<?php
$query = mysql_query("SELECT comments.id, comments.content, users.name, 
users.photo FROM comments, users WHERE comments.article_id = '".$get_id."' 
AND comments.parent_id = 0 AND comments.user_id = users.id");
while($res = mysql_fetch_assoc($query))
{
  $id = $res['id'];
  $content = $res['content'];
  $name = $res['name'];
  $photo = $res['photo'];

  echo $photo;
  echo $name;
  echo $content;

  $query2 = mysql_query("SELECT comments.id, comments.content, users.name, 
  users.photo FROM comments, users WHERE comments.article_id = '".$get_id."' 
AND comments.parent_id = '".$id."' AND comments.user_id = users.id");
  while($res2 = mysql_fetch_assoc($query2))
  {
    $id2 = $res2['id'];
    $content2 = $res2['content'];
    $name2 = $res2['name'];
    $photo2 = $res2['photo'];

    echo $photo2;
    echo $name2;
    echo $content2;
  }
}
?>

It doesn't work properly. It shows 1 parent and 1 child comment in each nest although there are several child comments.

How can I fix and minimize it? Can it be done by using only one query?

Thank you!

Answer 1

JOIN the table on itself.

Change your query to:

SELECT comments.id, comments.content, users.name, 
users.photo FROM comments JOIN users ON comments.user_id = users.id JOIN 
comments c ON comments.id = 
c.parent_id  WHERE 
comments.article_id = '".$get_id."' 
AND comments.parent_id = '".$id."'

You don't need the second query, here's the full code:

<?php

$query = mysql_query("SELECT comments.id, comments.content, users.name, 
users.photo FROM comments JOIN users ON comments.user_id = users.id JOIN 
comments c ON comments.id = 
c.parent_id  WHERE 
comments.article_id = '".$get_id."'");

while($res = mysql_fetch_assoc($query))
{
  $id = $res['id'];
  $content = $res['content'];
  $name = $res['name'];
  $photo = $res['photo'];

  echo $photo;
  echo $name;
  echo $content;
 } 

?>

Answer 2

Just use a JOIN to fetch the comments and with all the children.

SELECT users.id userID, users.name, users.photo , childrenComments.*,   
   parentComments.id cpId, parentComments.content cpContent,
   parentComments.user_id cpUser_id,parentComments.article_id cpArticleId
FROM users JOIN (SELECT * FROM Comment WHERE id=0) parentComments 
ON users.id=parentComments.user_id LEFT JOIN Comment childrenComments
ON parentComments.id=childrenComments.parent_id;

Then you can the loop through the result to print it appropriately. This would be better as you would have to run just a single query.