MySQL：选择具有最后一条记录的ID的组的计数

Question

Here is my table called logs :

id    package    log
====================
0     first      log0
1     first      log1
2     second     log2

And I want the query result to be like this:

package    count    last_log_id
===============================
first      2        1
second     1        2

So far, my searches led me to this:

SELECT package, COUNT(*) FROM logs GROUP BY package

This helped me getting the count of each group by package.

SELECT a1.package, COUNT(*),a1.id 
FROM logs a1 LEFT JOIN logs a2 
ON (a1.package = a2.package AND a1.id < a2.id) 
WHERE a2.id IS NULL 
GROUP BY a1.package

And this helped me getting the id of the last log, but the count is wrong!

package    count    last_log_id
===============================
first      1        1
second     1        2

Answer 1

I think your first attempt is correct, and you may use the MAX function to find the latest log id for each package:

SELECT
    package,
    COUNT(*) AS count,
    MAX(id) AS last_log_id
FROM logs
GROUP BY package;