SELECT on a to-be-determined table

Hi,

I'm a new at this. So please forgive if I mess up. Also, if there is
already a reference/tutorial somewhere, feel free to point me to it.

Here's my situation:
db=# select * from projects;
projid | projname
--------+----------
1 | cars
2 | houses
3 | pets
(3 rows)

db=# select * from cars;
carid | carname
-------+---------
1 | ford
2 | mazda
(2 rows)

db=# select * from houses;
houseid | housename
---------+-----------
1 | semi
2 | trailer
3 | mansion
(3 rows)

db=# select * from pets;
petid | petname
-------+---------
1 | dog
2 | cat
3 | bird
(3 rows)

Is it possible to do this:
Give me all the rows of the table whose project id is 2 (or whatever
projid).

Thanks