Hi,

I have three tables, two of which are missing a column:

	CREATE TABLE table1 (t1 TEXT);
	CREATE TABLE table2 (t2 TEXT);
	CREATE TABLE table3 (t3 TEXT, i3 INTEGER);

I am trying to create a view over these tables that defaults values for
non-existant columns to NULL.

	CREATE VIEW view1 (i, t) AS
	  SELECT t1, NULL FROM table1
	    UNION ALL
	  SELECT t2, NULL FROM table2
	    UNION ALL
	  SELECT t3, i3 FROM table3
	;

This fails with

	ERROR:  UNION types 'text' and 'integer' not matched

suggesting that NULL+NULL produces TEXT as type of the second column in
the union. The plain select (without CREATE VIEW) fails in the same way.

It works for two tables (NULL+INTEGER = INTEGER):

	CREATE VIEW view2 (i, t) AS
	  SELECT t1, NULL FROM table1
	    UNION ALL
	  SELECT t3, i3 FROM table3
	;

and of course with explicit casts

	CREATE VIEW view3 (i, t) AS
	  SELECT t1, NULL::integer FROM table1
	UNION ALL
	  SELECT t2, NULL::integer FROM table2
	UNION ALL
	  SELECT t3, i3 FROM table3
	;

Best wishes, Mike

PS: This is version()
    'PostgreSQL 7.3.1 on i686-pc-linux-gnu, compiled by GCC 2.95.4'.

-- 
Life is like a fire.                                  DI Michael Wildpaner
Flames which the passer-by forgets.                          Ph.D. Student
Ashes which the wind scatters.
A man lived.       -- Omar Khayyam


Fri, 31 Jan 2003 19:59:14 +0100 (CET)
Michael Wildpaner <mike@rainbow.studorg.tuwien.ac.at>
type problems during union: NULL+NULL produces TEXT