Mysqli examples

Comments:

• hahahahacker2009, 28.06.25 20:52

  Hello, I'm writing a forum software. All "threads" and "post" are stored in one table (they are called a message - msg). And a "thread" have the field relate_to=0, a "post" (comment to a "thread" have the field relate_to=id of the thread. I'm told that this will hurt performance, it have to read the whole table, mixed with threads and post, to find e.g threads to list on the main page. So will using mysql/mariadb partitions help? Or this is another delusion?

  Reply:

  Hello!

  Well, someone who told you that entire table will be read is not quite familiar with databases. There is a thing called index. All you need is to add index on relate_to. And so only relevant entries will be read from table.

  I assume, you are planning to display entire thread with a query like this?

  select * from msg WHERE id=? OR relate_to=?
  ORDER BY relate_to, datetime

  where, for both ? marks, the thread is will be used? If so, it's perfectly OK, and will never impact performance, only records that belong to certain thread will be read.

  The same goes for listing all threads:

  select * from msg WHERE relate_to=0

  will only read post messages from index and won't read replies.

  And no, partitions won't needed here. Your schema is very basic and would work for hundreds of thousands messages with most generic setup.

• Dude, 02.08.21 15:39

  Hello ,I need subcategory when I click in category(food,milk) then show me subcategory(food1,food2), Do you know how I can fix this?

• eljaydee, 12.04.20 04:28

  I cannot make this work: I have been told a million times to "review you query" but cannot find the issue. The query returns desired results on cmd line: <?php

       $dbhost = 'localhost:3306';
       $dbuser = 'root';
       $dbpass = 'oreo';
       $dbname = '650M';
       $conn = mysqli_connect($dbhost, $dbuser, $dbpass,$dbname);
  
       if(! $conn ) {
          die('Could not connect: ' . mysqli_error());
       }
       echo 'Connected successfully. <br> Here are the results of your query:<br><br>';
       $A=$_POST["A"];
       $B=$_POST["B"];
  
       $sql = 'SELECT * FROM blah1 WHERE A = $_POST["A"]=2 AND B = $_POST["B"]';
       $result = mysqli_query($conn, $sql);
  
       if (mysqli_num_rows($result) > 0) {
          while($row = mysqli_fetch_array($result)) {
             echo $row["blah2"]. ", &nbsp;";
          }
       } else {
          echo "0 results";
       }
       mysqli_close($conn);
        ?>