mySql Query running super slow - mysql

Question

I have seen a few post's regarding slow queries but none had the answer I'm hoping for.
I've been staring at this query for ages and for some reason cant see whats making this so damn slow dates such as 2022-01-01 > 2022-12-21 even taking 80 seconds....
So here is the query
SELECT
accounts.first_name,
accounts.last_name,
accounts.email,
(
SELECT
COUNT(ID)
FROM
customer_migration_details
WHERE
date_opened BETWEEN '2022-01-01' AND '2022-12-31' AND customer_migration_details.Assigned_to = accounts.email GROUP BY `accounts`.`email` LIMIT 1
) AS 'New Customers'
FROM
customer_migration_details
RIGHT JOIN accounts ON customer_migration_details.Assigned_to = accounts.email
WHERE
date_opened BETWEEN '2022-01-01' AND '2022-12-31' AND customer_migration_details.Assigned_to = accounts.email AND accounts.role LIKE '%Sales%'
GROUP BY
`accounts`.`email`
Heres the results
but here is the annoying part.
Showing rows 0 - 7 (8 total, Query took 109.5797 seconds.)
Theres got to be something im missing in the subquery maybe thats causing this to take so long.

Answer 1

acc: INDEX(email)
cmd: INDEX(Assigned_to, date_opened)
Having GROUP BY acc.email in the subquery seems wrong. And it may be unnecessary in the outer query.
Do not say COUNT(x) unless you need to avoid counting rows with x IS NULL. Instead, say simply COUNT(*).
If date_opened is a DATETIME, then you have excluded all but one second of New Years Eve.
LIKE with an initial wildcard is a performance problem. Are there multiple "roles" with "Sales" in them?
My brain gets scrambled when I see RIGHT JOIN. Can it be turned around to be a LEFT JOIN? Anyway, it seems to be an INNER JOIN.
Please provide EXPLAIN SELECT ...

Answer 2

Use a JOIN with GROUP BY or use a correlated sub-query, but not both at the same time.
SELECT
accounts.first_name,
accounts.last_name,
accounts.email,
COUNT(customer_migration_details.id) AS new_customers
FROM
accounts
LEFT JOIN
customer_migration_details
ON customer_migration_details.assigned_to = accounts.email
AND customer_migration_details.date_opened BETWEEN '2022-01-01' AND '2022-12-31'
WHERE
accounts.role LIKE '%Sales%'
GROUP BY
accounts.email
Or...
SELECT
accounts.first_name,
accounts.last_name,
accounts.email,
(
SELECT
COUNT(ID)
FROM
customer_migration_details
WHERE
date_opened BETWEEN '2022-01-01' AND '2022-12-31'
AND assigned_to = accounts.email
)
AS new_customers
FROM
accounts
WHERE
accounts.role LIKE '%Sales%'
Notes:
It's bad practice to put spaces, etc, in column names, so I changed New Customers to new_customers.
LIKE '%Sales%' can't use an index, so will scan each and every account row.