Question

此查询适用于更新字段this_count，其中包含特定用户（$ user_id）邀请的人数：

UPDATE table_one SET invitor_count = 
  (SELECT count(*) FROM table_one
      WHERE invitor = 
         (SELECT invite_name FROM table_one WHERE user_id = $user_id)
  )
WHERE user_id = $user_id;

我可以在一个查询中更新所有invitor_counts吗？我怎么能这样做？

表格结构

+---------+------------+------------+-------------+
| user_id | name       | invitor    | invite_name |
+---------+------------+------------+-------------+
|     215 | Susan B    | Alicia18   | Susan       |
|     217 | Alicia L   |            | Alicia18    |
+---------+------------+------------+-------------+

Answer 1

我认为以下查询对Oracle有帮助，我不确定MySQL是否有NVL或者还有其他类似的功能。

update table_one z
   set invitor_count =
          nvl((select count(*)
                 from table_one x
                 join table_one y on x.invite_name = y.invitor
                where x.user_id = z.user_id), 0)

Answer 2

UPDATE
      table_one AS t
  JOIN
      ( SELECT b.user_id, COUNT(*) AS cnt
        FROM 
              table_one a
          JOIN
              table_one AS b
            ON a.invitor = b.invite_name
        GROUP BY b.user_id
      ) AS grp
    ON grp.user_id = t.user_id

SET t.invitor_count = grp.cnt

在一个查询中计算更新

2 个答案: