select query for three joined table?

not sure if this is what you are looking for:

select 
a.a1,a.b1,b.b2,c.a3,c.b3
from
tableone a, tabletwo b, tablethree c
where
a.a1=123 and
a.a1 = b.a1 and
a.a1 = c.a1 ;