SQL查詢與來自另一個表計數（）

Question

我得到了下面的表格：

pictures 
------------------------------------ 
id 
name 
views 

votes 
------------------------------------ 
id 
user_id 
pic_id 

我想從一個查詢，這將使我每張圖片的ID，用圖片的意見得到的結果，從表votes總票用於特定pic_id

例如：

pictures.id，pictures.views，總票數

1 ------------ 78- -------- --------- 123

2 ------------ 23 ------------------- 69

等等...

我嘗試代碼：

SELECT `pictures`.`id`,`pictures`.`views`, COUNT(`votes`.`pic_id`) as votes 
FROM `pictures` 
JOIN `votes` 
ON `pictures`.`id` = `votes`.`pic_id` 

但它不給我我想要的reuslt。

Answer 1

您需要有GROUP BY條款。

使用LEFT JOIN將顯示錶pictures上的所有記錄，在表votes上有或沒有匹配記錄。

SELECT a.id, a.name, a.views, 
     COUNT(b.pic_id) TotalVotes 
FROM pictures a 
     LEFT JOIN votes b 
      ON a.id = b.pic_id 
GROUP BY a.id, a.name, a.views 

Answer 2

使用留下了一組功能加入，正常加入關鍵字意味着內部聯接，你需要一個左連接的一對多關係

SELECT `pictures`.`id`,`pictures`.`views`, COUNT(`votes`.`pic_id`) as votes 
FROM `pictures` 
LEFT JOIN `votes` 
ON `pictures`.`id` = `votes`.`pic_id` 
GROUP BY `pictures`.`id` 

Answer 3

試試這個：

SELECT `pictures`.`id`,`pictures`.`views`, COUNT(`votes`.`pic_id`) as votes 
FROM `pictures` 
JOIN `votes` 
ON `pictures`.`id` = `votes`.`pic_id` 
GROUP BY `votes`.`pic_id`; 

Answer 4

您需要使用GROUP BY子句這樣嘗試：

SELECT `pictures`.`id`,`pictures`.`views`, COUNT(`votes`.`pic_id`) as votes 
FROM `pictures` 
JOIN `votes` 
ON `pictures`.`id` = `votes`.`pic_id` 
group by `pictures`.`id`