I believe what I'm asking here is possible, but I haven't find a way yet :
Some cells in the result of my SQL SELECT-FROM-WHERE query are blank, and in DbVisualizer,
(SELECT COUNT(*) FROM table d2 WHERE *join-condition* AND *other condition*) = 1
FROM table d1
The problem in your query is the following ELSE part of the CASE expression:
In Oracle, an empty string is considered as NULL value. So, all you need to do is use something else instead of
For example, to use a space instead of NULL:
ELSE ' '
Update The issue is the DbVisualizer tool. OP is on version
8.0.12. Prior to version
9.2.8 it cannot show NULL as an empty string. However, as discussed in this forum, it has been fixed in DbVisualizer 9.2.8.