Databases Reference
In-Depth Information
One of the simplest uses for an outer join is to help see what is not part of an inner join!
For instance, the previous table shows us instantly that the second and fourth rows:
e
f
g
h
m
n
o
p
of table S are not involved in the natural join S
nat-join
T. Put another way, the values:
and:
are not present in any rows of table T.
5.3.10 Implementing Joins in Microsoft Access
Now let us consider how to implement the various types of joins in Microsoft Access.
The Access Query Design window makes it easy to create equi-joins. Of course, a natural
join is easily created from an appropriate equi-join by using a projection. Let us illustrate
this statement with an example.
Begin by creating the following two simple tables, S and T, shown in Table 5-12 and
Table 5-13.
Table 5-12.
T
he S table
A
1
A
2
a
b
c
d
e
f
Table 5-13. The T table
B
1
B
2
B
3
g
h
i
j
k
l
c
d
x
c
d
y
c
y
z
Let us create the equi-join:
