OK, you need any site with:
X and Y,
or
X,
or
Y
And you probably want a site "together" in one row.
Query1 will select all sites from table 1.
Query2 will select site and X from table 2.
Query3 will select siet and Y from table 3.
Query 4 will put it all together.
It will have Query1 on the...