Query getting alphabetical neighbours of chars in a strings

Question

10gR2
Hello,
Can anybody give me a Select for getting the neighbour-chars (by Ascii-Code) of a simple source-string for a certain number of iterations?
E.g. the source-string is "M" and the number of iterations is 7 then the Select's should give seven rows like:
"M"
"LM"
"MN"
"LMN"
"KLM"
"MNO"
"KLMNO"
"M" is the starting char; the next iteration gives the alphabetically preceding char "L" and concats with the starting char; the next iteration gives the alphabetical successor of the starting char (and concats it); the next iteration results the next the alphabetically preceding char of the most left-sided char of the last result; the next iteration gives the next alphabetical successor of the most right-sided char of the last iteration's result... and so on...
2nd example, when starting with "DE":
"DE"
"CDE"
"DEF".....
Any ideas / hints ?

Answer 1

Well, I don't see any business logic in that requirement, but here we go :
SQL> var letter varchar2(10)
SQL> var occ number
SQL> exec :letter:='M'
PL/SQL procedure successfully completed.
SQL> exec :occ:=7
PL/SQL procedure successfully completed.
SQL> select str
  2  from   (select lvl,
  3                 decode(lv,1,(select replace(max(sys_connect_by_path(chr(ascii(letter)-(nb-level+1)),',')),',')||letter from dual connect by level <= nb),
  4                           2,letter||(select replace(max(sys_connect_by_path(chr(ascii(substr(letter,-1,1))+level),',')),',') from dual connect by level <= nb),
  5                             (select replace(max(sys_connect_by_path(chr(ascii(letter)-(nb-level+1)),',')),',')||letter from dual connect by level <= nb)
  6                             ||(select replace(max(sys_connect_by_path(chr(ascii(substr(letter,-1,1))+level),',')),',') from dual connect by level <= nb)) str
  7          from   (select letter, level lvl, mod(level,3) lv, sum(decode(mod(level,3),1,1)) over (order by level) nb
  8                  from   (select :letter letter, :occ occ from dual)
  9                  connect by level <= occ-1)
10          where :occ > 1
11          union all
12          select 0,:letter from dual where :occ>0)
13  order by lvl;
STR
M
LM
MN
LMN
KLM
MNO
KLMNO
7 rows selected.
SQL> exec :letter:='DE'
PL/SQL procedure successfully completed.
SQL> exec :occ:=3
PL/SQL procedure successfully completed.
SQL> /
STR
DE
CDE
DEF
SQL> exec :letter:='DE'
PL/SQL procedure successfully completed.
SQL> exec :occ:=4
PL/SQL procedure successfully completed.
SQL> /
STR
DE
CDE
DEF
CDEF
SQL>Nicolas.
adding a WHERE clauses to support occ=1 or occ=0
Edited by: N. Gasparotto on Dec 22, 2008 4:34 PM