Question

我有一个MySQL查询，它选择当前用户的朋友创建的内容，并按相反的时间顺序列出该内容。

    SELECT node.nid AS nid,
   node.created AS node_created
 FROM node node 
 LEFT JOIN user_relationships user_relationships ON node.uid = user_relationships.requestee_id
 LEFT JOIN users users_user_relationships ON user_relationships.requestee_id = users_user_relationships.uid
 WHERE (node.status <> 0) AND (node.type in ('drigg', 'blog_post')) AND (user_relationships.requester_id = 1)
   ORDER BY node_created DESC

如何“扩展”此查询，以便除了节点之外还列出注释？

这是评论表的结构：

cid（评论ID）
uid（发表评论的用户的ID）
时间戳（使用相同的UNIX日期格式为“节点创建”列来自上面的节点表）

现在，查询抓取了当前用户与好友的所有“节点”。我希望它还能抓住当前用户与好友的所有评论。然后我想根据它们的创建日期以DESC顺序列出这些节点和注释。

看来我需要在select语句中添加更多内容，但我不确定是什么。

Answer 1

您可以使用UNION ALL来合并两个查询的结果：

SELECT nodeid, commentid, created FROM (
    SELECT node.nid AS nodeid, NULL as commentid, node.created AS created
    FROM node node 
    LEFT JOIN user_relationships user_relationships ON node.uid = user_relationships.requestee_id
    LEFT JOIN users users_user_relationships ON user_relationships.requestee_id = users_user_relationships.uid
    WHERE (node.status <> 0) AND (node.type in ('drigg', 'blog_post')) AND (user_relationships.requester_id = 1)
    UNION ALL
    SELECT NULL as nodeid, comment.cid AS commentid, comment.timestamp AS created
    FROM node node 
    LEFT JOIN user_relationships user_relationships ON node.uid = user_relationships.requestee_id
    LEFT JOIN users users_user_relationships ON user_relationships.requestee_id = users_user_relationships.uid
    WHERE (node.status <> 0) AND (node.type in ('drigg', 'blog_post')) AND (user_relationships.requester_id = 1)
)
ORDER BY created DESC

Answer 2

现在，查询抓取了当前用户与好友的所有“节点”。我希望它还能抓住当前用户与好友的所有评论。然后我想根据它们的创建日期以DESC顺序列出这些节点和注释。

使用：

   SELECT n.nid,
          COALESCE(c.timestamp, n.created) AS coalesced_timestamp,
          c.comment
     FROM NODE n
LEFT JOIN USER_RELATIONSHIPS ur ON ur.requestee_id = n.uid
LEFT JOIN USERS u ON u.uid = ur.requestee_id
LEFT JOIN COMMENT c ON c.uid = u.uid
                   AND c.nid = n.nid
    WHERE n.status <> 0 
      AND n.type in ('drigg', 'blog_post') 
      AND ur.requester_id = 1
 ORDER BY coalesced_timestamp DESC

那是based on the ERD listed here。

使表名别与表名本身相同或更长没有多大意义。

扩展mySQL查询以包含更多内容

2 个答案: