Calculating SUM() results from subqueries into a total - mysql

Question

My brain is starting to hurt with this query and I would appreciate some guidance. What I am trying to get as the result of this query are three values: attendanceScore, lootScore, and totalScore (attendanceScore - lootScore).
Attendance is tracked across three tables: attendance, attendancelog, and attendancevalues.
attendance records an individual's attendance status attached to an attendancelog record. There are types of attendance such as "attended", "missed", and "called out".
attendancelog is the parent record which records the event type, title and date as well as who logged the attendance and when.
attendancevalues is a config table that matches the attendance type from attendance and the event type from attendancelog and returns a configurable value FLOAT.
Loot is tracked across two tables: loot and loottypes.
loot logs each individual item, who received it and when and what type of loot it was (Primary, Secondary, Free-for-all).
loottypes is a config table that takes the type from loot and returns a configurable cost FLOAT.
After some work I have come up with a working query to get attendanceScore and lootScore:
SELECT
(SELECT SUM(t3.`value`)
FROM `attendance` t1
INNER JOIN `attendancelog` t2
ON t2.`id` = t1.`attendancelog_id`
INNER JOIN `attendancevalues` t3
ON t3.`eventtype_id` = t2.`type` AND t3.`attendancetype_id` = t1.`type`
WHERE t1.`user_id` = 3) as attendanceScore,
(SELECT SUM(t2.`cost`)
FROM `loot` t1
INNER JOIN `loottypes` t2
ON t2.`id` = t1.`type`
WHERE t1.`user_id` = 3) as lootScore
I know this doesn't work, but I tried to add (attendanceScore - lootScore) to the query but it says those fields are not available. That is ultimately what I need to complete the query.
I can get the result I want by copying each of the subqueries directly into (attendanceScore - lootScore) but it is just absolutely hideous and I'm sure unnecessary:
SELECT
(SELECT SUM(t3.`value`)
FROM `attendance` t1
INNER JOIN `attendancelog` t2
ON t2.`id` = t1.`attendancelog_id`
INNER JOIN `attendancevalues` t3
ON t3.`eventtype_id` = t2.`type` AND t3.`attendancetype_id` = t1.`type`
WHERE t1.`user_id` = 3) as attendanceScore,
(SELECT SUM(t2.`cost`)
FROM `loot` t1
INNER JOIN `loottypes` t2
ON t2.`id` = t1.`type`
WHERE t1.`user_id` = 3) as lootScore,
(
(SELECT SUM(t3.`value`)
FROM `attendance` t1
INNER JOIN `attendancelog` t2
ON t2.`id` = t1.`attendancelog_id`
INNER JOIN `attendancevalues` t3
ON t3.`eventtype_id` = t2.`type` AND t3.`attendancetype_id` = t1.`type`
WHERE t1.`user_id` = 3) - (SELECT SUM(t2.`cost`)
FROM `loot` t1
INNER JOIN `loottypes` t2
ON t2.`id` = t1.`type`
WHERE t1.`user_id` = 3)
) as totalScore
Could someone help me understand what methods to use for cleaning this up into something more streamlined and efficient?

Answer 1

You may use an inline view
SELECT attendanceScore,
lootScore,
attendanceScore - lootScore as totalScore
FROM
(
SELECT
(
SELECT SUM(t3.`value`)
FROM `attendance` t1
INNER JOIN `attendancelog` t2
ON t2.`id` = t1.`attendancelog_id`
INNER JOIN `attendancevalues` t3
ON t3.`eventtype_id` = t2.`type` AND t3.`attendancetype_id` = t1.`type`
WHERE t1.`user_id` = 3
) as attendanceScore,
(
SELECT SUM(t2.`cost`)
FROM `loot` t1
INNER JOIN `loottypes` t2 ON t2.`id` = t1.`type`
WHERE t1.`user_id` = 3) as lootScore
) t