Using Wildcards Efficiently With Equals Or LIKE

Is it possible to use wildcards with an equals statement? Such as
SELECT * FROM Table WHERE City = '%' AND State='Ca'
Bascially just stating where city equals anything...
I know you can do it with a LIKE statement such as...
SELECT * FROM Table WHERE City LIKE '%' AND State='Ca'
but is that very efficient?
The reason I want to do this is because I want to programmitcally
set the city, so just ommiting it won't work


Also, using City LIKE '%' seems to not include NULL...is there anyway
to include NULL as well as anything else?

Thanks for your help!