I installed Zabbix 2.2.6 LTS and unixODBC through yum, but after I've created an ODBC monitoring item to monitor MySQL database according to this tutorial:
https://www.zabbix.com/documentation/2.2/manual/config/items/itemtypes/odbc_checks

I found that the ODBC monitoring item cannot collect any data from database, the log files of zabbix server and agent seem to be all right and no error happend. But strangely, if I installed Zabbix 2.2.6 LTS from sources instead of installing from packages, the ODBC monitoring item works fine!

I've added my install steps and log files of zabbix server/agent in attachments, as explained below:
1. Install Zabbix 2.2.6 From Package.html: my install steps (from packages)
2. zabbix_server.log: log file of zabbix server
3. zabbix_agentd.log: log file of zabbix agent