Question

我有一个名为quotes的表：

id date       content
80 2012-06-03 This is the first quote.
81 2012-06-05 Lorem Ipsum.

一张名为rating的表：

rid uid qid rating
1   4   80  -1
2   4   81  1

uid字段是指进行该评级的登录用户。报价网站仅供登录用户使用，我希望能够向当前用户显示报价，包括指示报价当前评级的信息，是否对报价进行评级，如果是，他们评价了什么它作为。评级可以是-1或1.引号与提交它们的用户无关。

如果我只想获取一个引号，我执行此查询（例如引用80和用户4）：

SELECT
  q.id AS qid, q.content, q.date,
  COALESCE(SUM(r.rating), 0) AS rating,
    (SELECT COALESCE(rating, 0) FROM ratings WHERE qid = 80 AND uid = 4 LIMIT 1)
      AS user_rated
  FROM quotes q
  LEFT JOIN ratings r ON q.id = r.qid
  WHERE q.id = 80
  GROUP BY q.id

我如何修改它以显示多个报价（即不只是报价ID 80），但保留user_rated和评级信息？

非常感谢！

Answer 1

SELECT
  q.id AS qid,
  q.content,
  q.date,
  COALESCE(SUM(r.rating), 0) AS rating,
  COALESCE(SUM(IF(r.uid = 4, r.rating, NULL)), 0) AS user_rated
FROM quotes q
LEFT JOIN ratings r ON q.id = r.qid
GROUP BY q.id

多个联接以收集用户评级？

1 个答案: