MS ACCESS SQL：如何进行嵌套计数

Question

I am trying to count the number of messages userid = 1 did and then COUNT the number of messages of all the other userid and print out the names of the people where the number of messages = the number of messages userid = 1 has.

So I need to do a nested count. I have 2 tables for this. Messages and User.

For example:

SELECT COUNT(*)
FROM MESSAGES
WHERE user_id = 1

And the result is 2. Then I need

SELECT COUNT(*)
FROM MESSAGES
WHERE COUNT(*) = 2

How do I do a nested count for this so I can do something like

SELECT USER.user_name
FROM MESSAGES INNER JOIN USER ON MESSAGES.user_id = USER.user_id
WHERE COUNT(*) = (    
SELECT COUNT(*)
FROM MESSAGES
WHERE user_id = 1
)

The above example doesn't work for me. I am using MsAccess. Any help will be appreciated. Thank you.

Answer 1

Try using HAVING syntax

SELECT USER.user_name
FROM MESSAGES INNER JOIN USER ON MESSAGES.user_id = USER.user_id
GROUP BY MESSAGES.user_id, USER.user_name
HAVING COUNT(*) = (    
SELECT COUNT(*)
FROM MESSAGES
WHERE user_id = 1
)