MySQL查询列出不同的值？

Question

我无法使MySQL查询正常工作。 我想查询每个唯一'srcmac'（源MAC地址）的最新条目。 我可以用它来使用LINQ-MSSQL

    table.Where(g=> g.Srcintf != "port1")
         .GroupBy(p=> p.Srcmac)
         .Select(f=> f.First());

这是一些示例数据

itime       ap  srcintf     srcip       srcmac          srcssid user
1558943089      port1       10.x.xx.189                 username
1558943089      port1       10.x.xx.189                 username
1558943089  ARC5    ARCFREE     192.xxx.xx.8    34:ab:xx:xx:e5:94   ARCFREE 
1558943089      port1       10.x.x.13           
1558943089  ARC3    ARCFREE     192.xxx.xx.143  b4:18:xx:xx:fa:d0   ARCFREE 
1558943089  Outside STAFF-RF    172.xxx.x.2 8c:83:xx:xx:85:f0   STAFF   username
1558943089      port1       10.xx.xxx.174                   username
1558943089  Outside PUBLIC-RF   192.xxx.x.32                PUBLIC  
1558943089      port1       10.x.xx.238                 username
1558943089      port1       10.x.xx.28                  username
1558943089      port1       10.x.xx.28                  username
1558943089  ARC5    ARCFREE     192.xx.xx.8 34:ab:xx:xx:e5:94   ARCFREE 

但我没有将它转换为MySQL。 这就是我到目前为止所拥有的

    select p1.srcmac, from_itime(p1.itime), p1.srcip, p1.user, p1.srcintf, 
       p1.srcssid
       FROM $log p1
       INNER JOIN
       (
         SELECT max(from_itime(itime)) MaxPostDate, srcmac
         FROM $log
         where ( ( lower(`srcintf`) != lower('port1')))
         GROUP BY srcmac
       ) p2
       ON p1.srcmac = p2.srcmac
          AND from_itime(p1.itime) = p2.MaxPostDate
          WHERE ( ( lower(p1.srcintf) != lower('port1')))
       order by from_itime(p1.itime) desc

我得到的转储是

srcmac          from_itime      srcip       user    srcintf srcssid
34:ab:37:xx:xx:94   2019-05-28 04:43:29 192.xxx.xx.8        ARCFREE ARCFREE
34:ab:37:xx:xx:94   2019-05-28 04:43:29 192.xxx.xx.8        ARCFREE ARCFREE
34:ab:37:xx:xx:94   2019-05-28 04:43:29 192.xxx.xx.8        ARCFREE ARCFREE
4a:0b:b2:xx:xx:db   2019-05-28 04:43:26 192.xxx.xx.115      ARCFREE ARCFREE
58:d5:6e:xx:xx:c5   2019-05-28 04:43:24 172.xx.x.5  XPUSER  STAFF-R STAFF