在codeigniter中添加两个查询的计数？

Question

我有4张桌子 我查询： -  1.活动：有活动ID  2. activity_specialties：有活动ID和专业  用户：专业  4.列出项目

II查询：

1. 活动：有活动ID
2. icd10_assignments：activity_assignment_id

我必须从I查询和II查询中找到计数 并添加这些计数结果以查找总结果  我的列是活动ID和总计数 我的两个疑问是 1）

SELECT `activity`.`activity_id`, count(distinct users.id) as user_id
FROM (`activity`)
JOIN `activity_specialties` ON `activity`.`activity_id` = `activity_specialties`.`activity_id`
LEFT JOIN `users` ON `users`.`specialty`= `activity_specialties`.`specialties_id`
WHERE `activity_category` =  'Online CME Activities'
GROUP BY `activity`.`activity_id`

2）

SELECT `activity`.`activity_id`, count(icd10_assignments.id) as assign_id
FROM (`activity`)
JOIN `icd10_assignments` 
ON `activity`.`activity_id`= `icd10_assignments`.`activity_assignment_id`
WHERE `activity_category` =  'Online CME Activities'
GROUP BY `activity`.`activity_id`