MySQL optimized performance for two large tables with same index - mysql

Question

I have two tables with huge amount of data in them (~1.8mil in the main one, ~1.2mil in the secondary one), as follows:
subscriber_table (id, name, email, country, account_status, ...)
subscriber_payment_table (id, subscriber_id, payment_type, payment_credential)
My end goal is having a table, containing all the users and their payment tables (null if non existing), up to yesterday, and with account_status = 1 (active)
Mot all subscribers have a corresponding subscriber_payment, so using an INNER JOIN isn't a viable option, and using a LEFT JOIN has me end up with SQL timing out my query after 2 hrs after much processing effort.
SELECT
`subscribers`.`id` AS `id`,
`subscribers`.`email` AS `email`,
`subscribers`.`name` AS `name`,
`subscribers`.`geoloc_country` AS `country`,
`subscribers_payment`.`payment_type` AS `paymentType`,
`subscribers_payment`.`payment_credential` AS `paymentCredential`
`subscribers`.`create_datetime` AS `createdAt`
FROM
`subscribers`
LEFT JOIN
`subscribers_payment` ON (`subscribers_payment`.`subscriberId` = `subscribers`.`id`)
WHERE
`subscribers`.`account_status` = 1
AND DATE_FORMAT(CAST(`subscribers`.`create_datetime` AS DATE), '%Y-%m-%d') < curdate())
As mentioned, this query takes too much time and ends up timing out and not working.
I've also considered having a UNION, between "All the Subscribers" and "Subscribers with Payment".
(
SELECT
`subscribers`.`id` AS `id`,
`subscribers`.`email` AS `email`,
`subscribers`.`name` AS `name`,
`subscribers`.`geoloc_country` AS `country`,
null AS `paymentType`,
null AS `paymentCredential`
`subscribers`.`create_datetime` AS `createdAt`
FROM
`subscribers`
WHERE
`subscribers`.`account_status` = 1
AND DATE_FORMAT(CAST(`subscribers`.`create_datetime` AS DATE), '%Y-%m-%d') < curdate()))
UNION
(
SELECT
`subscribers`.`id` AS `id`,
`subscribers`.`email` AS `email`,
`subscribers`.`name` AS `name`,
`subscribers`.`geoloc_country` AS `country`,
`subscribers_payment`.`payment_type` AS `paymentType`,
`subscribers_payment`.`payment_credential` AS `paymentCredential`
`subscribers`.`create_datetime` AS `createdAt`
FROM
`subscribers`
INNERJOIN
`subscribers_payment` ON (`subscribers_payment`.`subscriberId` = `subscribers`.`id`)
WHERE
`subscribers`.`account_status` = 1
AND DATE_FORMAT(CAST(`subscribers`.`create_datetime` AS DATE), '%Y-%m-%d') < curdate()))
The problem with that current implementation is that I'm getting duplicate queries (I'm using a UNION but it's not grouping my results together and removing non-distinct values, that's because I have a different value in the paymentType and paymentCredential columns)
This query runs in about ~2mins, so this is more feasible for me. I just need to eliminate duplicate records.. unless there's a wiser option here
Disclaimer: we're using MyISAM tables, so having foreign keys to speed up the queries is a no-go.

Answer 1

For this query:
SELECT . . .
FROM subscribers s LEFT JOIN
subscribers_payment sp
ON sp.subscriberId = s.id
WHERE s.account_status = 1 AND
s.create_datetime < curdate();
Then, you want an index on subscribers(account_status, create_datetime, id) and on subscribers_payment(subscriberId).
I am guessing that the index on subscriber_payment is missing, which explains the performance problems.
Notes:
Use table aliases -- they make the query easier to write and read.
There should be no need to convert a datetime to a string for comparison purposes.
There is no need to use backticks for all identifiers. They just make the query harder to write and read.