I've the following table structures

Users id

Types id isBool

UsersTypes userid types

I want to select all the UserTypes based on id and isBool.

I tried this query

var q = from usertype in usertypes
        from type in types
        where type.isBool == false
        where userstypes.user == id
        select usertype;

But this did not work as expected. My questions are:

1. Why?
2. Is there any difference in using the join on syntax vs where, where vs where cond1 && cond2? My understanding is query optimizer will optimize.
3. Is there any difference in using where cond1 == var1 && cond2 == var2 with and without the parenthesis? This seems peculiar that it is possible to build this without parenthesis
4. What type of query do I need in this case? I can see that I could do a subquery or use a group but not 100% sure if it is required. An example might be helpful. I'm thinking a subquery may be required in this case.