Name of the recursive view to be created or replaced.
For information about naming database objects, see SQL Fundamentals, B035-1141.
If view_name is not fully qualified, the default database is used.
- Containing database or user for view_name if something other than the current database or user.
- Mandatory name of a view column or column set. If more than one column is specified, list their names in the order in which each is to be displayed for the view.
- An introduction to the view definition.
Example: A Simple Recursive View
This example uses the following base table as its base to build a simple recursive review definition with a counter to control the possibility of infinite recursion:
This view is designed to answer questions such as the following: Which parts are required to build part 01?
Notice that as written, this query does not really answer the question because there might be more than 100 levels in the data. Strictly speaking, the question this request asks is this: Which parts, up to a maximum of 100 levels, are required to build part 01?
The recursive view definition is as follows:
CREATE RECURSIVE VIEW rpl (part, subpart, quantity, depth) AS ( SELECT root.part, root.subpart, root.quantity, 0 AS depth FROM partlist AS root WHERE root.part = '01' UNION ALL SELECT child.part, child.subpart, child.quantity, parent.depth + 1 FROM rpl AS parent, partlist AS child WHERE parent.subpart = child.part AND parent.depth <= 100);
The query to answer the question of which parts are required to build part 01 is the following SELECT request:
SELECT part, subpart, quantity FROM rpl ORDER BY part, subpart, quantity;
The result set for this query is the following.
Example: Simple REPLACE RECURSIVE VIEW
The following example replaces the existing definition for the recursive view named rec with the specified SQL code:
REPLACE RECURSIVE VIEW rec(p, mycount) AS ( SELECT n, 0 AS mycount FROM t WHERE n = 1 UNION ALL SELECT rec.p, rec.mycount + 1 FROM t, rec WHERE rec.p = t.n AND rec.mycount <= 20