一个基本的sql-query示例

Question

我有两张桌子:

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

我应该在NEWS上选择(*)所有值,并在NEWS_VOTES表上计算投票,其中news.id和news_votes.new_id是相同的.

更清楚的解释是:

1. 我在NEWS表上选择所有值.
2. 根据"id"值,我还选择:

负面投票:

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

正面投票:

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

我需要在一个查询中执行此操作.

网站上的输出将是"这条新闻得到57张正面投票和67张反对票".

谢谢.

PS.我用MYSQL.

Answer 1

假设正面投票有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