Select time from view

Question

i have a doubt as will a select based on a view will take more time than a select on 2 tables with a union.
View will be:-
create view1 as
select column1 from table1
union
select column1 from table2
so, will a
select * from view1
take more time than a
select column1 from table1
union
select column1 from table2
Please help in solving the doubt as it is urgent.
regards.

Answer 1

If it's that urgent why didn't you just rustle up a test case for yourself? You could have done that in the time it took you to post, let alone wait for my slow fingers to type one up and compose this reply. We are all volunteers here and there's no SLA.
Here is a test case. Obviously the stats are different, that's because of the data in the buffer cache, but the EXPLAIN PLAN is identical (except for the VIEW bit), so the two queries should execute in a similar timeframe.
Cheers, APC
SQL> SET autotrace TRACEONLY
SQL> SELECT col1 FROM t_10K
  2  UNION
  3  SELECT col1 FROM t_5k1
  4  /
10000 rows selected.
Execution Plan
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=43 Card=15000 Bytes=
          60000)
   1    0   SORT (UNIQUE) (Cost=43 Card=15000 Bytes=60000)
   2    1     UNION-ALL
   3    2       INDEX (FAST FULL SCAN) OF 'T10K_PK' (UNIQUE) (Cost=3 C
          ard=10000 Bytes=40000)
   4    2       TABLE ACCESS (FULL) OF 'T_5K1' (Cost=3 Card=5000 Bytes
          =20000)
Statistics
        750  recursive calls
          0  db block gets
        213  consistent gets
         71  physical reads
          0  redo size
     132870  bytes sent via SQL*Net to client
       7825  bytes received via SQL*Net from client
        668  SQL*Net roundtrips to/from client
         16  sorts (memory)
          0  sorts (disk)
      10000  rows processed
SQL> CREATE VIEW v1 AS
  2  SELECT col1 FROM t_10K
  3  UNION
  4  SELECT col1 FROM t_5k1
  5  /
View created.
SQL> SELECT * FROM v1
  2  /
10000 rows selected.
Execution Plan
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=43 Card=15000 Bytes=
          195000)
   1    0   VIEW OF 'V1' (Cost=43 Card=15000 Bytes=195000)
   2    1     SORT (UNIQUE) (Cost=43 Card=15000 Bytes=60000)
   3    2       UNION-ALL
   4    3         INDEX (FAST FULL SCAN) OF 'T10K_PK' (UNIQUE) (Cost=3
           Card=10000 Bytes=40000)
   5    3         TABLE ACCESS (FULL) OF 'T_5K1' (Cost=3 Card=5000 Byt
          es=20000)
Statistics
         19  recursive calls
          0  db block gets
         54  consistent gets
          0  physical reads
          0  redo size
     132870  bytes sent via SQL*Net to client
       7825  bytes received via SQL*Net from client
        668  SQL*Net roundtrips to/from client
          3  sorts (memory)
          0  sorts (disk)
      10000  rows processed
SQL>