Databases Reference
In-Depth Information
The second query, in step 3, uses a
SELECT
DISTINCT
statement, and the corresponding
execution plan is shown in the next screenshot. We can see that no sort operation occurs,
except for a single
HASH
UNIQUE
step after a Full Table Scan operation.
The last query, in step 4, executes a
GROUP
BY
operation and an aggregate function
COUNT(*)
to show the number of customers for each city.
