Merge meta table with main table - php

Question

I have two tables, a main one, and one that supports the main table, very very similar to what wordpress has, posts and posts_meta.
Main table:
id
title,
content
id | title | content
1 | one | content one
2 | two | content two
Meta table:
id
item_id
key
value
id | item_id | key | value
1 | 1 | template | single
2 | 1 | group | top
1 | 2 | template | page
2 | 2 | group | bottom
And my goal is, in the end, have an array with the data from the main table, merged with the meta table. example:
$data = array(
array(
'id' => 1,
'title' => 'one',
'content' => 'content one',
'template' => 'single',
'group' => 'top'
),
array(
'id' => 2,
'title' => 'two',
'content' => 'content two',
'template' => 'page',
'group' => 'bottom'
)
);
What is the best way to achieve this in a way that preforms good?
I am using PDO to connect to my database, and how Im doing right now is, I first query the data on the first table, and then for each result, i query the meta table, I use prepared statements for this, since it's suposed to be fast, but even so, it's harming the performance of my script.
Thank you

Answer 1

Instead of querying meta table for each result from first query
you should extract the ids from the first result:
$rows = q('SELECT * FROM posts');
$byIds = [];
foreach ($rows as &$row)
{
$byIds[$row['id']] =& $row;
}
and run second query:
$rows2 = q('SELECT * FROM posts_meta WHERE item_id IN (' . implode(',', array_keys($byIds)) . ')');
Then loop the results in PHP and merge with first query results.
foreach ($rows2 as $row2)
{
$byIds[$row2['item_id']][$row2['key']] = $row2['value'];
}
You have your merged results in $rows variable now:
var_dump($rows);
This way you will have only 2 db requests.
Please note that i have used $byIds as array of references so i dont have to search row with specific id in second loop. This way order of elements in $rows are preserved.