about the star ...

Select * is bad... But it's not about the star, stupid! http://t.co/f3QslyYWCr 1 — prevents index-only scans 2 — bloats memory footprint

— SQL Performance Tips (@SQLPerfTips) February 24, 2015

The X-Series - 1 - SQL Pattern Matching

How to solve sudoku using Oracle Sql

Code found here:

with x( s, ind ) as
( select sud, instr( sud, ' ' )
  from ( select
  '53  7    '||
  '6  195   '||
  ' 98    6 '||
  '8   6   3'||
  '4  8 3  1'||
  '7   2   6'||
  ' 6    28 '||
  '   419  5'||
  '    8  79'  sud from dual )
  union all
  select substr( s, 1, ind - 1 ) || z || substr( s, ind + 1 )
       , instr( s, ' ', ind + 1 )
  from x
     , ( select to_char( rownum ) z
         from dual
         connect by rownum <= 9
       ) z
  where ind > 0
  and not exists ( select null
                   from ( select rownum lp
                          from dual
                          connect by rownum <= 9
                        )
                   where z = substr( s, trunc( ( ind - 1 ) / 9 ) * 9 + lp, 1 )
                   or    z = substr( s, mod( ind - 1, 9 ) - 8 + lp * 9, 1 )
                   or    z = substr( s, mod( trunc( ( ind - 1 ) / 3 ), 3 ) * 3
                                      + trunc( ( ind - 1 ) / 27 ) * 27 + lp
                                      + trunc( ( lp - 1 ) / 3 ) * 6
                                   , 1 )
                 )
)
select s
from x
where ind = 0
/