MySQL 5.7 查询以根据发送和响应日期擦除消息内容

Question

I'm having issues writing a query to erase the content of "inactive messages". Erasing the content is just replacing the content of the message with "erased".

A message is considered inactive when:

1. The sent date < NOW - 720 days
2. AND the message response date < NOW - 720 days

This would be easy if I had the message response date, but I don't. The only thing I have, is the "reply to message ID". The response date on a message would be the sent date of the LAST response message.

If message with ID 3 is a reply to message with ID 2 which was a reply to message with ID 1, the response date of message with ID 1 would be the sent date of message with ID 3.

Here is the table:

I tried this query to get all the "last" replies to messages but I'm not sure this will help me.

SELECT id, replyToMessage_id, sentDate
from Message OuterReference
where not exists (select 1 from Message where replyToMessage_id = OuterReference.ID)

Thanks in advance for your help!

Answer 1

Check this

DELETE t1
FROM Message t1
LEFT JOIN ( SELECT replyToMessage_id, MAX(sentDate) MaxSentDate
            FROM Message t2
            GROUP BY replyToMessage_id ) t3 ON t3.replyToMessage_id IN (t1.id, t1.replyToMessage_id)
WHERE COALESCE(t3.MaxSentDate, t1.SentDate) < CURRENT_DATE - INTERVAL 2 YEAR

Subquery gets last responce date per message.

Joining condition joins the most last responce to the message and to all its responces.

Condition checks that this last responce date (for the messages which have no responces - the date of the message itself) it too old for to be removed.

The query assumes that responce date cannot be earlier than message date.