Refactoring multiple mysql queries into 1 - php

Question

I am currently developing a system which generates various reports for a client and i need pointing in the direction in-order to achieve what i need.
The current situation is that i need to produce an overview of tasks which are outstanding (and some details about what is remaining).
So far i have created a list of all tasks so far (including information about the customer), this was achieved in the following query:
SELECT `fusion_repairs`.*, `fusion_customers`.*
FROM `fusion_repairs`
RIGHT JOIN `fusion_customers`
ON `fusion_repairs`.`customer_id` = `fusion_customers`.`customer_id`
ORDER BY `fusion_repairs`.`repair_id`
DESC LIMIT 20
Ideally i need to be able to check to see if the customer has been emailed about the task (fusion_mail table). If there are no mail records found for this task then i still want to show it (so another right join is out of the question.
I also need to do the same with the fusion_response table to check to see if the customer has sent in a response. If they haven't then i still want to display the task anyway.
Obviously i know i can achieve this by running a query within the main select query, but this doesn't sit well in my head. Is there a way i can do this in 1 query instead?
Thank you.

Answer 1

Change your query structure to use left joins only - essentially the same as a right join but then not having to swap between left and right join.
The fact you right-joined customers onto repairs tells me customers is the main table so now we can say get me everything from customers, join in repairs if a record exists.
SELECT `fusion_repairs`.*, `fusion_customers`.*
FROM `fusion_customers`
LEFT OUTER JOIN `fusion_repairs` ON `fusion_repairs`.`customer_id` = `fusion_customers`.`customer_id`
ORDER BY `fusion_repairs`.`repair_id`
DESC LIMIT 20
Here we can use left outer join to see if we have any mail, if not, do not remove the row and the same with response
SELECT `fusion_repairs`.*, `fusion_customers`.*
FROM `fusion_customers`
LEFT OUTER JOIN `fusion_repairs` ON `fusion_repairs`.`customer_id` = `fusion_customers`.`customer_id`
LEFT OUTER JOIN `fusion_mail` ON `fusion_mail`.`repair_id` = `fusion_repairs`.`repair_id`
LEFT OUTER JOIN `fusion_response` ON `fusion_response`.`repair_id` = `fusion_repairs`.`repair_id`
ORDER BY `fusion_repairs`.`repair_id`
DESC LIMIT 20
Now my question is.. What do you want to be returned? If there are 5 mail records then there will be 5 records for the 1 repair record. Do you just want a yes/no tick just to say they have then maybe a correlated subquery in the main select is actually what you want or a group by and count the number of mail inside a case to tick.
Let me know what you want as your output to finish the query up.
EDIT:
I've made an update to the query to take into account the information you gave me. Please note I have no idea how you want to output the final result so I just made a guess! Let me know if this solves it otherwise back to the drawing board for me!
SELECT fusion_repairs.*,
fusion_customers.*,
CONCAT( CASE WHEN fusionMail.mail_type_A > 0 THEN 'displayA' ELSE '' END,
CASE WHEN fusionMail.mail_type_B > 0 THEN 'displayB' ELSE '' END,
CASE WHEN fusionMail.mail_type_C > 0 THEN 'displayC' ELSE '' END) as email_font_awesome_icon,
CONCAT( CASE WHEN fusionResponse.response_status_A > 0 THEN 'displayA' ELSE '' END,
CASE WHEN fusionResponse.response_status_B > 0 THEN 'displayB' ELSE '' END,
CASE WHEN fusionResponse.response_status_C > 0 THEN 'displayC' ELSE '' END) as response_font_awesome_icon
FROM fusion_customers
LEFT OUTER JOIN fusion_repairs ON fusion_repairs.customer_id = fusion_customers.customer_id
LEFT OUTER JOIN (
SELECT repair_id,
SUM(CASE WHEN mail_type = 1 THEN 1 else 0 END) AS mail_type_A,
SUM(CASE WHEN mail_type = 2 THEN 1 else 0 END) AS mail_type_B,
SUM(CASE WHEN mail_type = 3 THEN 1 else 0 END) AS mail_type_C
FROM fusion_mail
GROUP BY repair_id
) fusionMail ON fusionMail.repair_id = fusion_repairs.repair_id
LEFT OUTER JOIN (
SELECT repair_id,
SUM(CASE WHEN response_status = 1 THEN 1 else 0 END) AS response_status_A,
SUM(CASE WHEN response_status = 2 THEN 1 else 0 END) AS response_status_B,
SUM(CASE WHEN response_status = 3 THEN 1 else 0 END) AS response_status_C
FROM fusion_response
GROUP BY repair_id
) fusionResponse ON fusionResponse.repair_id = fusion_repairs.repair_id