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
  execute stm using 9,4,'ABA';
  
  drop table tree;