Question

I want some advice on structuring some (basic) php code.

I need to display data from a table in different places. The rows that need to be displayed in each section can be identified by a flag.

I’m not sure if the best way to do this is to go to the database once and seperate the data into 2 variables as I loop through it or if I should go to the database twice, using sql to call only the data I need each time.

For those who want to see it in code:

Method A:

// Create and execute a MySQL query
function tasks_not_done(){
        // Open a PDO dtabase connection
        $link = new PDO(DB_INFO, DB_USER, DB_PASS);

        $sql = " SELECT title, created_date
                FROM todos
                WHERE list_id = ? AND checked = '0'
                ORDER BY created_date DESC";
        $stmt = $link->prepare($sql);
        $stmt->execute(array($_REQUEST['list_id']));

        // loop throught all the rows
        while($row = $stmt->fetch()) {
            $date = strtotime($row['created_date']);
            $date = date('d/m/y' , $date);
            echo '<div class="task">' . "\n";
            echo '<span class="taskcdtate">' .$date . '</span>'. '<span class="tasktitle"> ' . $row['title'] . ' </span>' . "\n";
            echo '</div>';

            }
       $stmt->closeCursor();
}

Method B

function tasks_all(){
       // Open a PDO dtabase connection
       $link = new PDO(DB_INFO, DB_USER, DB_PASS);

       $sql = " SELECT title, created_date, checked
                FROM todos
                WHERE list_id = ?
                ORDER BY created_date DESC";
        $stmt = $link->prepare($sql);
        $stmt->execute(array($_REQUEST['list_id']));

        // loop throught all the rows
        $tasks['not_done'] = "";
        $tasks['done'] = "";

        while($row = $stmt->fetch("FETCH_ASSOC")) {
            $date = strtotime($row['created_date']);
            $date = date('d/m/y' , $date);

            if($row['checked'] =='0'){
                $tasks['not_done'] .= '<div class="task">' . "\n";
                $tasks['not_done'] .='<span class="taskcdtate">' .$date . '</span>'. '<span class="tasktitle"> ' . $row['title'] . ' </span>' . "\n";
                $tasks['not_done'] .='</div>';
                } elseif ($row['checked'] =='1') {
                $tasks['done'] .= '<div class="task">' . "\n" .
                $tasks['done'] .='<span class="taskcdtate">' .$date . '</span>'. '<span class="tasktitle"> ' . $row['title'] . ' </span>' . "\n";
                $tasks['done'] .='</div>';
                }

            }
       $stmt->closeCursor();
       return $tasks;
}

thanks

Answer 1

There is no right answer to this kind of question, but I can give you some pointers.

My general rule is: get the data you need when you need it. But there are a lot of things that could affect this.

1. Will you always use data from both queries ? if yes, you should get all in one query. If Never, meaning they exclude each other, the answer is no.
2. If you always need query 1, and sometimes query, you have to make a few more considerations. Does query 1 take much more time if you include query 2? How often do you need query 2, almost always or almost never.
3. What happens if someone else updates data at the same time. Let’s say you get both at once, and someone else updates data that affects query 2. This means you’re using outdated data. If you fetch the data when you need it, you might get correct updated data.