Create dummy variables in PostgreSQL - postgresql

Question

Is it possible to create a dummy variable when querying
For instance the query below will give me only the observations that satisfy the var1 conditions. I also want the remaining observations but with some kind of tag on it (0/1, indicator values would be sufficient)
SELECT distinct ON (id) id,var1,var2,var3
FROM table
where var2 = ANY('{blue,yellow}');
Have
+-----+------+--------+------+
| id | Var1 | Var2 | Var3 |
+-----+------+--------+------+
| 345 | 12 | Blue | 3456 |
| 345 | 12 | Red | 2134 |
| 346 | 45 | Blue | 3451 |
| 347 | 25 | yellow | 1526 |
+-----+------+--------+------+
Want
+-----+------+--------+------+--------------------+
| id | Var1 | Var2 | Var3 | Indicator variable |
+-----+------+--------+------+--------------------+
| 345 | 12 | Blue | 3456 | 1 |
| 345 | 12 | Red | 2134 | 0 |
| 346 | 45 | Blue | 3451 | 1 |
| 347 | 25 | yellow | 1526 | 1 |
+-----+------+--------+------+--------------------+

Answer 1

Instead of a expression in where you can use an expression in select output expressions:
=> select a, a = any('{1,2,3,5,7}') as asmallprime
from generate_series(1,10) as a;
a | asmallprime
----+-------------
1 | t
2 | t
3 | t
4 | f
5 | t
6 | f
7 | t
8 | f
9 | f
10 | f
(10 rows)

Answer 2

Tometzky's answer is sufficient, but if you want something more complex you can also use CASE statements.
Tometzky's example using CASE with an extra indicator
SELECT a, CASE WHEN a = any('{1,2,3,5,7}') THEN 'YES'
WHEN a = any('{4,9}') THEN 'SQUARE' ELSE 'NO' END as asmallprime
FROM generate_series(1,10) as a;