Hi,

If this log format is the same for all messages, you can write a custom filter with store-matches flag. It uses pcre expression by default.
I just created one for you:

filter f_router {
    message('^\w+\s+\d+\s+\d+:\d+:\d+ (?<my_host>\d+.\d+.\d+.\d+).+<(?<my_username>[^>]*)>[^(]*\((?<my_userip>\d+.\d+.\d+.\d+):(?<my_userport>\d+)->(?<my_wanip>\d+.\d+.\d+.\d+):(?<my_wanport>\d+)\)->(?<my_dstip>\d+.\d+.\d+.\d+):(?<my_dstport>\d+).*'
            flags(store-matches));
};

log {
    source(s_test);
    filter(f_router);
    destination(d_sql);
};

The values are available with the $ sign like:
file("/dev/stdout" template("$my_host $my_username $my_userip $my_userport $my_wanip $my_wanport $my_dstip $my_dstport \n"));

[2020-01-08T15:39:48.259469] Outgoing message; message='101.11.11.252 pppoe-zaib 172.16.0.2 49482 101.11.11.252 2224 58.27.130.12 443 \x0a'
101.11.11.252 pppoe-zaib 172.16.0.2 49482 101.11.11.252 2224 58.27.130.12 443

Regards,
Attila
From: syslog-ng <syslog-ng-bounces@lists.balabit.hu> on behalf of JAHANZAIB SYED <aacable@hotmail.com>
Sent: Wednesday, January 8, 2020 9:59 AM
To: syslog-ng@lists.balabit.hu <syslog-ng@lists.balabit.hu>
Subject: [syslog-ng] customized rewrite to mysql in syslog-ng
 
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I have syslog-ng version 3.25.1 on Ubuntu 18.04 server. All logs from remote mikrotik router device is stored in local file and in mysql DB as well. I want to know if there is any method in which we can customize the incoming message and write it to mysql table in different columns.

Incoming message example:
Jan  8 13:50:24 101.11.11.252 firewall,info forward: in:<pppoe-zaib> out:ether1-agp-wan, src-mac d0:bf:9c:f7:88:76, proto UDP, 172.16.0.2:49466->172.217.19.10:443, NAT (172.16.0.2:49466->101.11.11.252:2223)->172.217.19.10:443, len 1023

Jan  8 13:53:09 101.11.11.252 firewall,info forward: in:<pppoe-zaib> out:ether1-agp-wan, src-mac d0:bf:9c:f7:88:76, proto UDP, 172.16.0.2:49482->58.27.130.12:443, NAT (172.16.0.2:49482->101.11.11.252:2224)->58.27.130.12:443, len 1152

The relevant part that I want to store is 
HOSTNAME, DATETIME, AND message part 172.16.0.2:49482->101.11.11.252:2224)->58.27.130.12:443 * into following tables

hostname datatime username userip userport wanip wanport dst-ip dst-port
101.11.11.252 xxxx pppoe-zaib 172.16.0.2 49466 101.11.11.252 2223 172.217.19.10 443



Regards,
SYED JAHANZAIB