how to install qmake on windows code example

Example: qmake install windows

qmake is built by default when Qt is built.

but berfore that 
Installing qmake manually
Before building Qt manually the following environment variables must be set:

QMAKESPEC
This must be set to the platform and compiler combination that you are using on your system.
For example, if you are using Windows and Microsoft Visual Studio, you would set this environment variable to win32-msvc. If you are using Solaris and g++, you would set this environment variable to solaris-g++.

The following is a list of environment variables available to choose from when setting QMAKESPEC:

aix-64 hpux-cc irix-032 netbsd-g++ solaris-cc unixware7-g++ aix-g++ hpux-g++ linux-cxx openbsd-g++ solaris-g++ win32-borland aix-xlc hpux-n64 linux-g++ openunix-cc sunos-g++ win32-g++ bsdi-g++ hpux-o64 linux-icc qnx-g++ tru64-cxx win32-msvc dgux-g++ hurd-g++ linux-kcc reliant-64 tru64-g++ win32-watc freebsd-g++ irix-64 macx-pbuilder reliant-cds ultrix-g++ win32-visa hpux-acc irix-g++ macx-g++ sco-g++ unixware-g hpux-acc irix-n32 solaris-64 unixware7-cc

The environment variable should be set to qws/envvar where envvar is one of the following:

linux-arm-g++ linux-generic-g++ linux-mips-g++ linux-x86-g++ linux-freebsd-g++ linux-ipaq-g++ linux-solaris-g++ qnx-rtp-g++

QTDIR
This must be set to where Qt is (or will be) installed. For example, c:\qt and \local\qt

Once the environment variables are set go into the qmake directory, $QTDIR/qmake, e.g. C:\qt\qmake. Now run make or nmake depending on your compiler.

When the make has completed, qmake is ready for use.