MySQL查詢統計

Question

我在做SQL查詢來獲取從DB值，DB結構如下...

fcats

| id | title | section | 
+----+--------+---------+ 
| 1 | test | gd  | 
+----+--------+---------+ 

ftopics

| id | title | cat_id | 
+----+--------+---------+ 
| 1 | test1 | 1  | 
+----+--------+---------+ 

fposts

| id | post | topic_id | 
+----+-------+----------+ 
| 1 | post | 1  | 
+----+-------+----------+ 

我想主題和給定類職位的總人數，並使用下面的查詢......

SELECT id, title (SELECT count(id) FROM ftopics WHERE cat_id = id) AS total_topics FROM fcats WHERE section = "gd" 

，並讓正確的結果總的話題，但我怎樣才能獲得職位總數所有類別，我有點迷惑，請幫我寫這個查詢。謝謝。

Answer 1

試試這個：

SELECT 
    t.id, 
    t.title, 
    COUNT(f.id) + COUNT(p.id) AS total 
FROM fcats t 
LEFT OUTER JOIN ftopics f 
    ON f.cat_id = t.id 
LEFT OUTER JOIN fposts p 
    ON p.cat_id = t.id 
WHERE t.section = "gd" 
GROUP BY t.id, t.title 

Answer 2

SELECT 
    t.id, 
    t.title, 
COUNT(f.id) AS total_topics, 
(SELECT COUNT(p.id) FROM fposts WHERE topic_id = t.id) total_posts 
FROM fcats t 
INNER JOIN ftopics f 
    ON f.cat_id = t.id 

WHERE t.section = "gd" 
GROUP BY t.id, t.title 

不知道這是正確的語法，更新其他答案代碼嘗試回答你的兩個總計請求。