我得到了一个“ Subquery returns more than 1 row “运行要返回两个子查询结果的查询时出错。为什么返回多行是这里的一个问题，我如何才能绕过这个问题？
数据表和相关字段如下所示： Accounts 身份证件 Meetings 帐户\u id
分配的用户id
开始日期 Users 身份证件
姓
会议分配给帐户和用户。我正在尝试创建一个表，该表将显示会议开始日期在不同日期范围内的每个帐户的每个指定用户的会议数量。日期范围应排列在同一行中，作为带有以下标题的表格：
账户|用户名|未来1-31天会议|未来31-60天会议
如图所示：

.
我的问题是：

SELECT
(SELECT
    a.name
  FROM
    accounts AS a
  JOIN
    meetings AS m ON a.id = m.account_id
    AND date_start BETWEEN CURDATE() AND DATE_ADD(CURDATE(),INTERVAL 60 DAY)
  JOIN
    users AS u ON m.assigned_user_id = u.id
  WHERE
    m.status = 'Planned'
    AND m.deleted = 0
GROUP BY a.id, u.id) AS 'Account',
(SELECT
    u.last_name
  FROM
    accounts AS a
  JOIN
    meetings AS m ON a.id = m.account_id
    AND date_start BETWEEN CURDATE() AND DATE_ADD(CURDATE(),INTERVAL 60 DAY)
  JOIN
    users AS u ON m.assigned_user_id = u.id
WHERE
    m.status = 'Planned'
    AND m.deleted = 0
GROUP BY a.id, u.id) AS 'Name',
(SELECT
    COUNT(m.id)
  FROM
    accounts AS a
  JOIN
    meetings AS m ON a.id = m.account_id
    AND date_start BETWEEN CURDATE() AND DATE_ADD(CURDATE(),INTERVAL 30 DAY)
  JOIN
    users AS u ON m.assigned_user_id = u.id
  WHERE
    m.status = 'Planned'
    AND m.deleted = 0
GROUP BY a.id, u.id) AS 'Meetings 1-30 days',
(SELECT
    COUNT(m.id)
  FROM
    accounts AS a2
  JOIN
    meetings AS m ON a.id = m.account_id
    AND m.date_start BETWEEN DATE_ADD(CURDATE(),INTERVAL 31 DAY) AND DATE_ADD(CURDATE(),INTERVAL 60 DAY)
  JOIN
    users AS u ON m.assigned_user_id = u.id
  WHERE
    m.status = 'Planned'
    AND m.deleted = 0
GROUP BY a.id, u.id) AS 'Meetings 31-60 days'

包含帐户名和用户名的列必须作为子查询添加，以避免“ Operand should contain 1 column(s) “错误。与会议计数相对应的列必须是子查询，因为联接表的任何一行都不能同时适合这两个日期范围。每个子查询在单独运行时返回预期结果。但我明白了” Subquery returns more than 1 row “当子查询如图所示放在一起时。我试着给每个子查询分配不同的别名，但是没有用。