ORA-01790: expression must have same datatype as corresponding expression

Hi,

the following SQL doesn't work:

select a.num1, a.num2, a.num3, a.num4, a.num5, a.num6, a.num7, a.num8 from table1
union all
select a.num1, a.num2, a.num3, a.num4, NULL as num5, NULL as num6, NULL as num7, NULL num8
from table2;

I need a merged view on both tables, and as table2 does not contain num5 to num8, I want to insert the columns with the value NULL. But that doesn't work, I get the following Oracle error message:

ORA-01790: expression must have same datatype as corresponding expression

I could use 0 (zero) instead of NULL, but as zero represents a valid value in my program, I decided to use NULL.
Is there any way to state the datatype in my select statement?

Thank you for your hints,
Regards
Sebastian Received on Tue Jul 02 2002 - 06:22:00 CDT