Select a specific column based on another column's value

Question

I have a table like this

ID | Type | Val0 | Val1
1  |  0   |  A   | NULL
2  |  1   | NULL |  B

I need to select Val0 when the type

Answer 1

The way I read this, you need to use UNION:

SELECT a.val0
  FROM TABLE a
 WHERE a.type = 0
UNION ALL
SELECT a.val1
  FROM TABLE a
 WHERE a.type = 1
UNION ALL ...

UNION ALL doesn't remove duplicates, and is faster than UNION (because it removes duplicates).

Doing this dynamically is possible.