Define installed packages of specific Vendor

When lots of things are installed on a computer, it is sometimes difficult to define what are the installed packages of a specific vendor.
This is a little command allowing to get such Information :
rpm -qa --qf "%-30{NAME}\t%{VENDOR}\n" |grep -i VENDOR_NAME

VENDOR_NAME must be replaced by what you want ("Red Hat" for instance).

The opposite can be done. To define what are the installed packages which are not provided by a specific vendor :
rpm -qa --qf "%-30{NAME}\t%{VENDOR}\n" |grep -v VENDOR_NAME