How to build "dummy columns" for UNION?

Question

from what I understand "each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the columns in each SELECT statement must be in the same order." Well what if the first SELECT has more columns than the 2nd one can generate. Here's what I mean: let's say I want to

SELECT "City", "Country", "Continent" from table1  
UNION  
SELECT "City", "Country" from table2     

...let's say table 2 does not contain a column called "Continent" but for my needs it's fine for the records that come from table2 to have a blank or NULL in that column. I am using dashDB.

Answer 1

You can always add "virtual" columns:

SELECT "City", "Country", "Continent" from table1  
UNION  
SELECT "City", "Country", NULL AS "Continent" from table2 

Answer 2

Hi,
You can use,

 SELECT "City", "Country", "Continent" from table1  
UNION  
SELECT "City", "Country", ' ' as "Continent"  from table2

or

 SELECT "City", "Country", "Continent" from table1  
    UNION  
    SELECT 

"City", "Country", NULL as "Continent"  from table2

It considers "Continent" as null in table2