如何从MySQL到PHP以一对多关系处理数据

Question

I am using the following query to return data about a single habit.

A habit can have many steps and many comments.

When I run the following query it repeats the data for the habit for every step and comment there is.

        SELECT 
        habit_id, habit_user_id, habit_name, habit_category_id, habit_description, habit_target_user, habit_up_votes, habit_down_votes, 
        step_id, step_description, 
        comment_id, comment_user_id, comment_description
        FROM habits, steps, comments 
        WHERE habit_id = ? 
        AND habit_id = step_habit_id
        AND habit_id = comment_habit_id
        ORDER BY step_order

Example output (the ids should be enough to get an idea of what is going on):

habit_id    step_id    step_description    comment_id    comment_description
1           1          do x                1             this works great!
1           1          do x                2             Awful!
1           1          do x                3             nice job
1           2          then do y           1             this works great!
1           2          then do y           2             Awful!
1           2          then do y           3             nice job

I want to be able to take this returned data and have it in one array.

array("habit_id" => 1, "step_id" => array(1, 2), "comment_id" => array(1, 2, 3));

The only ways I can think of doing this are by either:

Executing 3 seperate queries 1 to get the habit data, 1 to get the steps for that habit and 1 to get the comments for that habit.

or

By using the above query as is and constructing a new array with the habit data and then looping through all the rows and constructing a new array for the steps and for the comments while at the same time making sure there are no duplicates added.

This sounds way too inefficient, can anyone suggest a better way either by modifying my query to provide PHP with more workable data or with some trick in PHP. I did at one point consider concatenating the data into arrays for the steps and comments within the query, but I thought this should be PHP's job to manipulate the data in such a way.

The reason why I want my data in this way is to return it to be used in an Angularjs application.

Answer 1

The query is fine as is. It's returning enough data for you to iterate through and build the array you want.

$data = array();

// could be any type of loop here. whatever returns data from your query
while($row=mysql_fetch_array($result)) {
    $data['habit_id'] = $row['habit_id'];

    // the in_array check ensures there are no dupes
    if (!in_array($row['step_id'], $data['step_id'])) {
        $data['step_id'][] = $row['step_id'];
    }
    if (!in_array($row['comment_id'], $data['comment_id'])) {
        $data['comment_id'][] = $row['comment_id'];
    }
}

This is going to be more efficient than three separate queries. Make sure your database is properly indexed. And check that you're using those indexes by running your query with EXPLAIN.

Answer 2

I would do this way. let me know if this solve your problems.

<?php

$test = NULL;
$test['habit_id']= $habitID; // I assume $habit is known;
$query = "SELECT * FROM steps
        WHERE habit_id = '".$habitID."';";
$result= mysql_query($query, $con);
while($row=mysql_fetch_array($result))
    $test['step_id'][]=$row['step_id'];

$query= "SELECT * FROM comments 
        WHERE habit_id = '".$habitID."';";
$result= mysql_query($query, $con);
while($row=mysql_fetch_array($result))
    $test['comment_id'][]=$row['comment_id'];

var_dump($test);

?>