SQL SELECT WHERE IN another SELECT with GROUP_CONCAT - sql

Question

Good Day,
I have 3 Tables - Ticket, Ticket Batch (Multiple Ticket Rows To One Batch) and Ticket Staff (Multiple Staff Rows To One Ticket) and wish to ultimately UPDATE the ticket_batch table with the COUNT of all staff working on tickets per ticket batch.
The tables with applicable columns look as follows
ticket:
| ticket_number | recon_number |
ticket_batch:
| recon_number |
ticket_staff:
| ticket_number |
So I have written the following SQL query to essentially first if I do get the COUNT:
SELECT COUNT(*)
FROM ticket_staf
WHERE ticket_staff.ticket_number IN (SELECT GROUP_CONCAT(ticket.ticket_number) FROM ticket WHERE ticket.recon_number = 1);
Which the query just keeps running, but when I execute the queries separately:
SELECT GROUP_CONCAT(ticket.ticket_number)
FROM ticket
WHERE ticket.recon_number = 1;
I get 5 ticket numbers within split seconds and if I paste that string in the other portion of the query:
SELECT COUNT(*)
FROM ticket_staff
WHERE ticket_staff.ticket_number IN (1451,1453,1968,4457,4458);
It returns the correct COUNT.
So ultimately I guess can I not write queries with GROUP_CONCATS into another SELECT WHERE IN? And how should I structure my query?
Thanks for reading :)

Answer 1

I prefer Inner join as follows:
SELECT COUNT(distinct ts.*)
FROM ticket_staff ts
LEFT JOIN ticket t
ON ts.ticket_number = t.ticket_number
WHERE t.recon_number = 1;

Answer 2

GROUP_CONCAT() doesn't look right. I suspect you are confusing a list of values for IN with a string. They are not the same thing.
In general, I would recommend EXISTS over IN anyway:
SELECT COUNT(*)
FROM ticket_staff ts
WHERE EXISTS (SELECT 1
FROM ticket t
WHERE ts.ticket_number = t.ticket_number AND
t.recon_number = 1
);
For this query, you want an index on ticket(ticket_number, recon_number). However, I am guessing that ticket(ticket_number) is the primary key, which is enough of an index by itself.