use test;

set @var_x= 'ABC';
set @var_x= NULL;

prepare __stmt_ph_ from "select 'blabla' as my_column 
                         from (select 1) as t1 where ? IS NULL" ;
# I miss here a result containing one row with 'blabla'  !!! 
execute __stmt_ph_ using @var_x ;

# statements for comparison
select 'blabla' as my_column 
from (select 1) as t1 where NULL IS NULL ;
select 'blabla' as my_column 
from (select 1) as t1 where @var_x IS NULL ;
prepare __stmt_uv_ from "select 'blabla' as my_column 
                         from (select 1) as t1 where @var_x IS NULL" ;
execute __stmt_uv_ ;