Tricky select statement ??

Question

Hello everybody,
can anyone helps me?
I have a table with 2 columns, e.g. .
A A5
A 5
B 5
C 5
D 5
D D5
Now, i will select:
If column 2 is the combination of column 1 and 5, then select this record and not the record with only 5. Doesn't exist the combination I will select the record with the only 5.
My result should look:
A A5
B 5
C 5
D D5.
Thanks.
Best Regards
Sandra Koenig

Answer 1

One way would be:
SQL> SELECT * FROM t;
C1    C2
A     A5
A     5
B     5
C     5
D     5
D     D5
SQL> SELECT c1, c2
  2  FROM t
  3  WHERE c2 = c1||'5'
  4  UNION ALL
  5  SELECT c1, c2
  6  FROM t o
  7  WHERE c2 = '5' and
  8        NOT EXISTS (SELECT 1
  9                    FROM t i
10                    WHERE o.c1 = i.c1 and
11                          i.c2 = i.c1||'5')
12  ORDER BY c1;
C1    C2
A     A5
B     5
C     5
D     D5Another, one-pass, way is:
SQL> SELECT c1, c2
  2  FROM (SELECT c1, c2,
  3               RANK() OVER (PARTITION BY c1 ORDER BY LENGTH(c2) DESC) rn
  4        FROM t
  5        WHERE c2 = '5' OR
  6              c2 = c1||'5')
  7  WHERE rn = 1;
C1    C2
A     A5
B     5
C     5
D     D5TTFN
John