page117
99
Figure 3-19.
CTE attribute pushdown disabled
The important point to note is the single table scan
TableScan2
showing the CTE is
resolved once and no filters are pushed down.
You will not experience the same behavior when explicitly referencing the same base
table
nation_baseline
as used within the earlier parent CTE.
WITH comment_list AS
(
SELECT n_comment
FROM nation_baseline
),
name_list AS
(
SELECT n_name
FROM nation_baseline
)
SELECT n_comment
ChapTer 3
The Query profiler