Need to develop a client based on the 5.5.x client lib.
Because of this, I need the related "devel rpm", which provides
the C header files, which are required for development.
The RPMs you are listing, only contain the libraries.

The RPM of interest is:
host:/media/SLE-11-SP4-SDK-DVD-x86_6408401/suse/x86_64 # ls *mysql*dev*
host:/media/SLE-11-SP4-SDK-DVD-x86_6408401/suse/x86_64 # rpm -qlp libmysqlclient-devel-5.0.96-0.6.1.x86_64.rpm

However, the SDK only provides the above shown 5.0.x devel rpm, although the
OS provides both, the 5.0.x client lib and the 5.5.x client lib.
The minor release is not of interest. It does not matter if 5.5.43 or 5.5.60.
But the major release must not differ.
I cannot develop a client based on the lib provided by libmysql55client_r18-32bit-5.5.43-0.7.3.x86_64.rpm
using the C header files provided by libmysqlclient-devel-5.0.96-0.6.1.x86_64.rpm.

In fact the SDK misses to provide something like: