Join Tables to find SUM for Points available and points completed - sql

Question

I have three tables: Achievements, Characters, and Character_Achievements table that store's the ID's of completed achievements and user id. I am looking to get each category, total amount of points possible and also the amount completed.
I am able to get each category and the amount of points possible but I am unsuccessful at retrieving the completed count as well.
I currently use this to get each category and the amount of points possible
SELECT achievements.category, SUM(points) AS Total
FROM achievements
GROUP BY achievements.category ORDER BY achievements._id asc
I get these results.
Category Total
Operations 50
Events 25
I can also get the amount of points completed
SELECT achievements.category, SUM(points) AS Completed
FROM achievements
LEFT JOIN character_achievements
ON character_achievements.achievements_id = achievements._id
LEFT JOIN character
ON character_achievements.character_id = character._id
WHERE character._id = '1'
which returns this but only the categories that are completed. How do I combine these two queries together.
Category Completed
Operations 50
Events 25
I've tried UNION but it does not return the results I need.
Here are my example tables
Achievements Table
Category Title Points
Operations Epic Enemies 25
Operations Explosive Conflict 25
Events Bounty Contract 25
Character_Achievements Table
Character Character_id Achievements_id
Operations 1 1
Events 1 3
The results I'm looking for would like this.
Results
Category Completed Total
Operations 25 50
Events 25 25
I am able

Answer 1

If I'm understanding your question correctly, you can use SUM with CASE:
SELECT a.category,
SUM(CASE WHEN ca.achievements_id is not null then points end) AS Completed,
SUM(points) Total
FROM achievements a
LEFT JOIN character_achievements ca
ON ca.achievements_id = a._id
GROUP BY a.category
ORDER BY a._id asc