Zählwerte in anderen Tabelle

Question

Ich habe zwei Tabellen = subjects und stats.

-- subjects --    
------------------   
| id | name |   
------------------   
| 1 | subjecta |   
| 2 | subjectb |  
| 3 | subjectc |   
| 4 | subjectd |   
| 5 | subjecte |   
| 6 | subjectf |   
| 7 | subjectg |  
| 8 | subjecth |   
| 9 | subjecte |  
| ... | subjectf |  
------------------  

-- stats -- 
----------------------------------- 
| user_id | subject_id | correct | 
----------------------------------- 
| 1  | 1  | false | 
| 1  | 1  | false | 
| 1  | 2  | false | 
| 4  | 3  | false | 
| 4  | 4  | false | 
| 4  | 5  | false | 
| 2  | 1  | true | 
| 2  | 1  | true | 
| 2  | 2  | false | 
| 2  | 2  | true | 
| 2  | 3  | false | 
--------------------------------- 

Was ich brauche, zum Beispiel für ein give user_id (wie 2), erhalten alle Fächer (von Fächern Tabelle) und für die, die er tun (von Statistiken) die Anzahl der richtig wahr/falsch wie dies:

-------------------------------------------------- 
| id | name  | correct true | correct false| 
----------------------------------|---------------- 
| 1 | subjecta |  2  |  0  | 
| 2 | subjectb |  1  |  1  | 
| 3 | subjectc |  0  |  1  | 
| 4 | subjectd |  0  |  0  | 
| 5 | subjecte |  0  |  0  | 
| 6 | subjectf |  0  |  0  | 
| 7 | subjectg |  0  |  0  | 
| 8 | subjecth |  0  |  0  | 
| 9 | subjecte |  0  |  0  | 
| ... | subjectf |  0  |  0  | 
----------------------------------|--------------| 

Ich habe keine Ahnung, was ich tun soll.

Answer 1

Sie können dies mit einem Join zwischen Ihren beiden Tabellen erreichen, zusammen mit einer bedingten Aggregation, um die Anzahl der richtigen und falschen Antworten zu ermitteln.

SELECT 
    t1.id, 
    t1.name, 
    SUM(CASE WHEN t2.correct = 'true' THEN 1 ELSE 0 END) AS correct_true, 
    SUM(CASE WHEN t2.correct = 'false' THEN 1 ELSE 0 END) AS correct_false 
FROM subjects t1 
LEFT JOIN stats t2 
    ON t1.id = t2.subject_id AND 
     t2.user_id = 2 
GROUP BY t1.id, t1.name 

Answer 2

select subjects.id, subjects.name, coalesce(t.correct_true, 0), coalesce(t.correct_false, 0) 
from subjects 
left join (
SELECT 
    subject_id, 
    SUM(CASE WHEN correct = 'true' THEN 1 ELSE 0 END) AS correct_true, 
    SUM(CASE WHEN correct = 'false' THEN 1 ELSE 0 END) AS correct_false 
    FROM stats 
    where user_id = 2 
    group by subject_id 
) t 
on subjects.id = t.subject_id