UNION ALL bug - 11g

Question

I have a strange bug with Oracle 11g. I was trying tu use Microsoft Entity Framework; the queries produced are a bit special and some of them are using UNION ALL in a way that produces an error.
Let us create this very very simple table (I used SQL Developer and let the default) :
CREATE TABLE "USER"."TABLE1"
( "COLUMN1" VARCHAR2(4000 BYTE),
"COLUMN2" NUMBER
Try this query, even without data :
SELECT * FROM(
SELECT NULL AS C1 FROM USER.TABLE1
UNION ALL
SELECT NULL AS C1 FROM USER.TABLE1
UNION ALL
SELECT COLUMN2 FROM USER.TABLE1
this produces a "*Expression must have same datatype as corresponding expression*" error !
Now if you do the same on COLUM1 of type VARCHAR2 :
SELECT * FROM(
SELECT NULL AS C1 FROM USER.TABLE1
UNION ALL
SELECT NULL AS C1 FROM USER.TABLE1
UNION ALL
SELECT COLUMN1 FROM USER.TABLE1
No error is raised, the query is executed normally.
Note that if you do :
SELECT * FROM(
SELECT NULL AS C1 FROM USER.TABLE1
UNION ALL
SELECT COLUMN2 FROM USER.TABLE1
no error is raised.
What's happening ??!!
Edited by: user5485007 on 12 sept. 2008 04:34

Answer 1

In 10.2.0.4:
SQL> CREATE TABLE t1
  2  ( "COLUMN1" VARCHAR2(4000 BYTE)
  3  , "COLUMN2" NUMBER
  4  )
  5  /
Table created.
SQL> SELECT * FROM(
  2  SELECT NULL AS C1 FROM t1
  3  UNION ALL
  4  SELECT NULL AS C1 FROM t1
  5  )
  6  UNION ALL
  7  SELECT COLUMN2 FROM t1
  8  /
SELECT * FROM(
ERROR at line 1:
ORA-01790: expression must have same datatype as corresponding expression
SQL> SELECT * FROM(
  2  SELECT NULL AS C1 FROM t1
  3  UNION ALL
  4  SELECT NULL AS C1 FROM t1
  5  )
  6  UNION ALL
  7  SELECT COLUMN1 FROM t1
  8  /
no rows selected
SQL> SELECT * FROM(
  2  SELECT NULL AS C1 FROM t1
  3  )
  4  UNION ALL
  5  SELECT COLUMN2 FROM t1
  6  /
no rows selectedThe same as the original poster on 11g ...
Regards,
Rob.