一個基本的SQL查詢例子

我有兩個表：一個基本的SQL查詢例子

NEWS (id, news_content) 
NEWS_VOTES (vote, news_id)

我應該選擇（*）對新聞的所有值，並且還指望NEWS_VOTES表投票，其中news.id和news_votes.new_id是相同。

更清晰一點的解釋是：

我選擇上NEWS表中的所有值。
根據「ID」的值，我也選擇：

反對票：

SELECT count(*) FROM NEWS_VOTES WHERE news_id = (same ID) AND vote = 0

贊成票：

SELECT count(*) FROM NEWS_VOTES WHERE news_id = (same ID) AND vote = 1

我必須這樣做在一個單一的查詢。

網站上的輸出將會像「這個消息得到57個正面票和67個反對票」。

謝謝。

Ps。我使用MYSQL。

來源

2012-01-03 Aristona

你如何區分正面和負面的投票？他們正在使用相同的查詢！：-O – 2012-01-03 10:30:31

負面和正面選票對'vote'有相同的價值？ – Matten 2012-01-03 10:30:43

試試聯盟... – duffymo 2012-01-03 10:30:56

假設贊成票有vote=1：

select 
    n.id, 
    n.news_content, 
    (select count(*) from news_votes where news_id=n.id and vote = 1) as positive_votes, 
    (select count(*) from news_votes where news_id=n.id and vote = 0) as negative_votes 
from news n

來源

2012-01-03 10:32:16 Matten

非常感謝。 :) – Aristona 2012-01-03 10:46:57

SELECT n.id, n.news_content, 
     COUNT(v1.vote) AS negative, 
     COUNT(v2.vote) AS positive 
FROM news n 
LEFT JOIN news_votes v1 ON v1.news_id = n.id 
LEFT JOIN news_votes v2 ON v2.news_id = n.id 
HAVING v1.vote = 0 AND HAVING v2.vote = 1 
GROUP BY v1.news_id, v2.news_id 
ORDER BY id DESC

來源

2012-01-03 10:33:33 Jules

select id, news_content, 
    coalesce(v.positive, 0) as positive, 
    coalesce(v.negative, 0) as negative 
from news n 
left join (
    select news_id, 
     sum(case when vote = 1 then 1 else 0 end) as positive, 
     sum(case when vote = 0 then 1 else 0 end) as negative 
    from news_votes 
    group by news_id 
) v on n.id = v.news_id

來源

2012-01-03 10:36:55

嘗試這一個 -

SELECT 
    n.*, 
    COUNT(IF(nv.vote = 1, 1, NULL)) Positive_Votes, 
    COUNT(IF(nv.vote = 0, 1, NULL)) Negative_Votes 
FROM news n 
    LEFT JOIN NEWS_VOTES nv 
    ON nv.news_id = n.id 
GROUP BY 
    n.id

哪裏投票= 1表示積極投票，以及投票= 0表示反對票。

來源

2012-01-03 10:37:59 Devart

選擇（SELECT FROM NEWS_VOTES COUNT（*）WHERE news_id =（相同的ID）和表決= 0）positive_votes，（SELECT COUNT（*）FROM NEWS_VOTES WHERE news_id =（相同的ID）和表決= 1）negative_votes 來自雙重;

來源

2012-01-03 11:31:53

一個基本的SQL查詢例子

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