What is it that you want to show?
If you want to show only data where there are matches, use inner join.
Select
a.Col1, a.Col2, b.Col1, b.Col2, b.Col3
from tableA a
INNER JOIN tableB b
on a.Col1 = b.Col2
If you want to show all matches, plus all rows from tableA, use a LEFT OUTER JOIN:
Select
a.Col1, a.Col2, b.Col1, b.Col2, b.Col3
from tableA a
LEFT OUTER JOIN tableB b
on a.Col1 = b.Col2