SQL Market Share

Greetings everyone,

Does anyone know if a reputable source has done market share
studies with the various
SQL servers out there in enterprise Web settings?

I'm trying to convince a company to have support for more than
Microsoft and Oracle servers
so I am looking for some numbers to back me up :-)

If anyone can help me with this, I would appreciate it.

I don't care too much if it includes all of the open-source SQL
servers out there,
just something to open their eyes.

Thanks
Dan Harrington