带有子查询的 MySQL 更新

Question

我有一个更新查询的恼人问题，我正在尝试开始工作...以下语句应该将 channels.media_view_count 更新为子查询的结果(对于所有 channel )。

UPDATE channels c
SET c.media_view_count = (
    SELECT SUM(t.view_count)
    FROM (
      SELECT DISTINCT m.viewkey, m.view_count
      FROM media m
      INNER JOIN participants p ON m.id = p.medium_id
      WHERE p.user_id = c.id AND m.is_viewable = 1
            AND (p.pending = 0)
      ) AS t
  );

子查询独立运行良好(当为 c.id 指定实际 ID 时，如 47778 或其他)，但是当我执行此语句时，我得到:

ERROR 1054 (42S22): Unknown column 'c.id' in 'where clause'

我想我可以从子查询中访问 channel 表(别名为 c)？我是不是遗漏了什么或者我完全错了？

感谢任何和所有的帮助:)

谢谢，

• 杰夫

Answer 1

UPDATE channels c, (
    SELECT t.user_id, SUM(t.view_count) cnt
    FROM (
      SELECT DISTINCT p.user_id, m.viewkey, m.view_count
      FROM media m
      INNER JOIN participants p ON m.id = p.medium_id
      WHERE m.is_viewable = 1
            AND (p.pending = 0)
      ) AS t GROUP BY t.user_id ) temp
SET c.media_view_count = temp.cnt
WHERE c.id =  temp.user_id

像这样尝试...虽然没有测试 :) ..
从概念上讲，它应该可以工作