QB

Auxiliary node that represents a subquery in a particular SQL statement.

A subquery can be any of the following operations:

• MERGE
• INSERT
• SELECT
• UPDATE
• DELETE
• SELECT with FOR UPDATE OF
• UPDATE WHERE CURRENT OF CURSOR
• DELETE WHERE CURRENT OF CURSOR
• TRUNCATE
• Table expression
• Correlated subselect or full select
• Non-correlated subselect or fullselect
• EXCEPT
• EXCEPT ALL
• EXCEPT
• EXCEPT ALL
• UNION
• UNION ALL

Notes:

• The query block node is the root of a subtree and represents the whole subquery.
• QBn denotes a query block node,where n represents the query block number.