sql query takes ages to complete - php

Question

I have two relational tables of which i both need data. The first (Main) table contains about 90k rows. The secondary table contains about 200k plus rows.
I need to add some data of the secondary table to the results i get from the first table currently i do this in two parts:
First: i select the required rows from the Main table this goes super fast.
$records = getData($conn, "
SELECT id
from Main
where contains_tags is not null
and contains_mediums is not null
and contains_techniques is not null
limit 100
");
-
Then i go over each record to add the extra data from the secondary table but this takes ages (1 min for 100 records 50min - 100 min for 5k records. In the end i need to run this query for about 5-10k rows of the Main table). Is there a way to speed this process up?
foreach ($records as $r => $record) {
$records[$r]['mediums'] = getData($conn, "SELECT medium from mediums where kleding_id = ".$record['id']."");
kleding_id = ".$record['id']."");
}
This is the desired output after both queries finish:
[1] => Array
(
[id] => 15
[mediums] => Array
(
[0] => Array
(
[medium] => wol
)
[1] => Array
(
[medium] => katoen
)
)
)
So my question is how to run this query structure efficiently in as little as time as possible.
the Main table look like this:
the Secondary table looks like this:
If anything is unclear let me know so i can clarify.

Answer 1

If you need improve performance
be sure you have a proper index table mediums column kleding_id
CREATE INDEX my_index ON mediums (kleding_id);
remember that limit (for not recent db version) normally work on the result ..a and not break after the first 100 is reached

Answer 2

You can do it in a single query. But it's for mysql Verison 5.7 & above.
SELECT id, GROUP_CONCAT(json_object('medium', mediums.medium))
FROM Main
LEFT JOIN mediums ON Main.id = mediums.kleding_id
WHERE contains_tags IS NOT NULL AND contains_mediums IS NOT NULL AND contains_techniques IS NOT NULL
GROUP BY Main.id
LIMIT 100
Also make sure you have a index on kleding_id.

Answer 3

There is no need to iterate over the first result and call the 2nd table multiple times. This will always be slow.
Try inner join to aggregate data from both tables in one sql statement.
SELECT
Main.id,
mediums.medium
from
Main
inner join mediums on
(
Main.id = mediums.kleding_id
)
where
contains_tags is not null
and contains_mediums is not null
and contains_techniques is not null limit 100;