string - Replacing "(null)" with blank cell in SQL query result -

i believe i'm asking here possible, haven't find way yet :

some cells in result of sql select-from-where query blank, , in dbvisualizer, (null) written inside. i'd display blank cell instead.
i've tried case-when , nvl operator, won't let me replace blank '', i'm forced use ' ' or 'message'.

i know delete these spaces or messages excel later, i'd know if there way directly dbvisualizer, instead of workaround.

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edit: here request looks :

select *things*,   case when      (select count(*) table d2 *join-condition* , *other condition*) = 1        (*sub-select query*)   else      ''   end   name,   *other things*   table d1   *something* 

thanks lot !

the problem in query following else part of case expression:

 else      '' 

in oracle, empty string considered null value. so, need use something else instead of ''.

for example, use space instead of null:

else     ' ' 

update issue dbvisualizer tool. op on version 8.0.12. prior version 9.2.8 cannot show null empty string. however, discussed in forum, has been fixed in dbvisualizer 9.2.8.