SQL selecting from multiple tables and ordering by certain conditions - php

Question

I have 2 tables, customer and tickets
I want to be able to select from the tickets table and order by:
tickets.priority then customer.category_priority then tickets.queue_time
I have this query:
SELECT t.*
from tickets t
JOIN customer c ON t.company = c.sequence
WHERE t.status <> 'Completed' AND t.queue = 'Y'
ORDER BY field(t.priority, 'Critical', 'High', 'Medium', 'Low'), t.queue_time ASC
which works great for the tickets.priority and tickets.queue_time
but im not sure how to incorporate the customer.category_priority
so in the customer table, i have columns with names like:
priority_computers
priority_telephone
priority_software
all INT fields and have a value of 0, 1 or 2
the row in tickets has a category column which is either Computers, Telephone, or Software and thats what needs to link to the above.
so, if a customer row has priority_computers of 2 and the tickets row is category = 'Computers' that would be at the top of the list because the customer record has the priority of 2 and it would also incorporate the other ORDER BY conditions
Examples:
Customers:
Company A priority_computers = 1
Company B priority_computers = 2
Company C priority_computers = 3
Example One:
Ticket 1 Company A priority = Medium category = Computers
queue_time = 2015-11-20 08:00
Ticket 2 Company B priority = Medium category = Computers
queue_time = 2015-11-20 10:00:00
Ticket 3 Company C priority = Medium category = Computers
queue_time = 2015-11-20 08:30:00
This should output in the following order:
Ticket 3
Ticket 2
Ticket 1
Example 2:
Ticket 1 Company B priority = High category = Computers
queue_time = 2015-11-20 12:00
Ticket 2 Company A priority = Medium category = Computers
queue_time = 2015-11-20 07:00:00
Ticket 3 Company C priority = Medium category = Computers
queue_time = 2015-11-20 07:00:00
This should output in the following order:
Ticket 1
Ticket 3
Ticket 2

Answer 1

If I understand this correctly, then your problem is that you have to match data with column names somehow.
customer.priority_computers for ticket.category = 'Computers'
customer.priority_telephone for ticket.category = 'Telephone'
customer.priority_software for ticket.category = 'Software'
This shows a database design flaw. There should be a customer_priority table instead with each row holding a customer, a category and the associated value. Then you could simply join.
As is, you must check data content and decide for a column to use in your query:
SELECT t.*
from tickets t
JOIN customer c ON t.company = c.sequence
WHERE t.status <> 'Completed' AND t.queue = 'Y'
ORDER BY field(t.priority, 'Critical', 'High', 'Medium', 'Low')
, case t.category
when 'Computers' then c.priority_computers
when 'Telephone' then c.priority_telephone
when 'Software' then c.priority_software
end
, t.queue_time ASC
Update: Here is a query you'd write, if you had a customer_priority table. You see, your query doesn't need to know what categories exist and how to treat them any longer.
SELECT t.*
from tickets t
JOIN customer c ON t.company = c.sequence
JOIN customer_priority cp ON cp.customer_id = c.sequence
AND cp.category = t.category
WHERE t.status <> 'Completed' AND t.queue = 'Y'
ORDER BY field(t.priority, 'Critical', 'High', 'Medium', 'Low')
, cp.priority_value
, t.queue_time ASC
Moreover: As mentioned, it is strange to have a table customer, but in tickets it's not called a customer, but a company, and in the customer table itself it's not called a customer number or ID either, but a sequence. This makes the queries less readable. I suggest, you change the names, if possible, so they are consistent.
Also your query shouldn't have to know what 'Critical' and 'High' means. There should be a table for priorities where each priority has a name and a value, so the query could simply pick the value and work with it without having to know anything else about the priorities.