[sql] Select a dummy column with a dummy value in SQL?

I have a table with the following

Table1
col1   col2
------------
 1      A 
 2      B
 3      C
 0      D

Result

col1   col2  col3
------------------
0       D     ABC

I am not sure how to go about writing the query , col1 and col2 can be selected by this

select col1, col2 from Table1 where col1 = 0;

How should I go about adding a col3 with value ABC.

If you meant just ABC as simple value, answer above is the one that works fine.

If you meant concatenation of values of rows that are not selected by your main query, you will need to use a subquery.

Something like this may work:

SELECT t1.col1, 
t1.col2, 
(SELECT GROUP_CONCAT(col2 SEPARATOR '') FROM  Table1 t2 WHERE t2.col1 != 0) as col3 
FROM Table1 t1
WHERE t1.col1 = 0;

Actual syntax maybe a bit off though