Evaluate Grouped ONCE-UNIQUE AGGREGATE.
Evaluate Ungrouped ONCE-UNIQUE AGGREGATE.
When the subquery includes distinct, the ONCE-UNIQUE aggregate indicates that duplicates are being eliminated:
select pub_name from publishers
where pub_id =
(select distinct titles.pub_id from titles
where publishers.pub_id = titles.pub_id
and price > $1000)
QUERY PLAN FOR STATEMENT 1 (at line 1).
STEP 1
The type of query is SELECT.
FROM TABLE
publishers
Nested iteration.
Table Scan.
Forward scan.
Positioning at start of table.
Run subquery 1 (at nesting level 1).
Using I/O Size 2 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.
NESTING LEVEL 1 SUBQUERIES FOR STATEMENT 1.
QUERY PLAN FOR SUBQUERY 1 (at nesting level 1 and at line 3).
Correlated Subquery.
Subquery under an EXPRESSION predicate.
STEP 1
The type of query is SELECT.
Evaluate Ungrouped ONCE-UNIQUE AGGREGATE.
FROM TABLE
titles
Nested iteration.
Index : pub_id_ix
Forward scan.
Positioning by key.
Keys are:
pub_id ASC
Using I/O Size 16 Kbytes for index leaf pages.
With LRU Buffer Replacement Strategy for index leaf pages.
Using I/O Size 2 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.
END OF QUERY PLAN FOR SUBQUERY 1.
