Databases Reference
In-Depth Information
In step 4, we use the
INTERSECT
operator to retrieve the last names which are in both
CUSTOMERS
and
MY_EMPLOYEES
tables. The corresponding execution plan is shown in
the following screenshot:
We can see that there are two full table scans of the
CUSTOMERS
and the
MY_EMPLOYEES
tables, followed by two
SORT
UNIQUE
operations required to compute the
INTERSECTION
between the two tables.
The same query can be expressed using a
JOIN
, as in step 5, using a
SELECT
DISTINCT
to mimic the behavior of the
INTERSECT
operator, and this removes duplicates.
