text: create table tree(id int,parentid int,text varchar(32));
  
  prepare stm from 'insert tree values(?,?,?);'
  execute stm using 1,null,'A'
  execute stm using 2,null,'B'
  execute stm using 3,1,'AA'
  execute stm using 4,1,'AB'
  execute stm using 5,2,'BA'
  execute stm using 6,2,'BB'
  execute stm using 7,3,'A--'
  execute stm using 8,3,'A--'
  deallocate prepare stm;
  
  prepare stm from 'update tree set text=''AA-'' where text=''A--'';'
  execute stm
  deallocate prepare stm;
  
  prepare stm from 'update tree set text=? where id=?;'
  execute stm using 'AAA',7
  execute stm using 'AAB',8
  deallocate prepare stm;
  
  prepare stm from 'select id,parentid,text,level from tree start with parentid is null connect by parentid=prior id order by id;'
  execute stm
  deallocate prepare stm;
  
  prepare stm from 'select id,parentid,text,level from tree where level=? start with parentid is null connect by parentid=prior id order by id;'
  execute stm using 2
  deallocate prepare stm;
  
  prepare stm from 'delete from tree where id>2'
  execute stm
  deallocate prepare stm;
  
  prepare stm from 'delete from tree where id=?'
  execute stm using 1
  execute stm using '2'
  deallocate prepare stm;
  
  drop table tree;