Outer join on query with OR clause

Question

hi all, i am having problem outerjoining a query with or clause
here is my data
WITH table1 AS
SELECT  'test' txt1, 'pak' txt2, 'ced' txt3, 'su' txt4 FROM dual UNION ALL
SELECT  null txt1, 'pak' txt2, 'ced2' txt3, 'su2' txt4 FROM dual UNION ALL
SELECT  null txt1, NULL txt2, 'ced3' txt3, 'su3' txt4 FROM dual UNION ALL
SELECT  null txt1, NULL txt2, null txt3, 'su3' txt4 FROM dual UNION ALL
SELECT  'text5' txt1, NULL txt2, null txt3, 'su3' txt4 FROM dual UNION ALL
SELECT  null txt1, NULL txt2, null txt3, null txt4 FROM dual
,table2 AS
SELECT 111 pid, 'test' txt1, 'pak4' txt2, 'ced' txt3, 'su' txt4 FROM dual UNION ALL
SELECT 222 pid, 'test1' txt1, 'pak' txt2, 'ced2' txt3, 'su2' txt4 FROM dual UNION ALL
SELECT 333 pid, 'test2' txt1, 'pak3' txt2, 'ced3' txt3, 'su4' txt4 FROM dual UNION ALL
  SELECT 444 pid, 'test2' txt1, 'pak3' txt2, 'ced4' txt3, 'su3' txt4 FROM dual
SELECT b.pid, a.*
from table1 a, table2 b
WHERE (a.txt1 = b.txt1 OR
       a.txt1 IS NULL AND a.txt2=b.txt2 OR
       Nvl(a.txt2, a.txt1) IS NULL AND a.txt3 = b.txt3 OR
       Nvl(a.txt2, a.txt1) IS NULL  AND a.txt3 IS NULL AND a.txt4 = b.txt4
       ) as you can see i am joining table1 and table 2. i am joining with txt1, if txt1 is null then join by txt2, if null then join by txt3 and so on.
the code above product this output
PID     TXT1     TXT2     TXT3     TXT4
===     ====     ===   ==== ====
111     test     pak      ced     su
222             pak      ced2     su2
333                     ced3     su3
444                          su3this output is partially correct. only 4 rows were display and two was left out
SELECT  'text5' txt1, NULL txt2, null txt3, 'su3' txt4 FROM dual UNION ALL
SELECT  null txt1, NULL txt2, null txt3, null txt4 FROM dual i tried using outer join but oracle complain that i cannot use outerjoin with OR clause.
can someone help modify my query to display the output below ?
PID     TXT1     TXT2     TXT3     TXT4
===    ====      ===   ====  ====
111     test     pak      ced     su
222             pak      ced2     su2
333                     ced3     su3
444                          su3
NULL  NULL   NULL    NULL   NULL
     test5

Answer 1

Not sure you can do it with the Oracle style outer joins, but wioth ANSI style joins it is simple, actually exactly as you had it.
SQL> set null null;
SQL> WITH table1 AS (
  2   SELECT  'test' txt1, 'pak' txt2, 'ced' txt3, 'su' txt4 FROM dual UNION ALL
  3   SELECT  null txt1, 'pak' txt2, 'ced2' txt3, 'su2' txt4 FROM dual UNION ALL
  4   SELECT  null txt1, NULL txt2, 'ced3' txt3, 'su3' txt4 FROM dual UNION ALL
  5   SELECT  null txt1, NULL txt2, null txt3, 'su3' txt4 FROM dual UNION ALL
  6   SELECT  'text5' txt1, NULL txt2, null txt3, 'su3' txt4 FROM dual UNION ALL
  7   SELECT  null txt1, NULL txt2, null txt3, null txt4 FROM dual),
  8  table2 AS (
  9   SELECT 111 pid, 'test' txt1, 'pak4' txt2, 'ced' txt3, 'su' txt4 FROM dual UNION ALL
10   SELECT 222 pid, 'test1' txt1, 'pak' txt2, 'ced2' txt3, 'su2' txt4 FROM dual UNION ALL
11   SELECT 333 pid, 'test2' txt1, 'pak3' txt2, 'ced3' txt3, 'su4' txt4 FROM dual UNION ALL
12   SELECT 444 pid, 'test2' txt1, 'pak3' txt2, 'ced4' txt3, 'su3' txt4 FROM dual)
13  SELECT b.pid, a.*
14  from table1 a
15     LEFT JOIN table2 b
16        ON (a.txt1 = b.txt1 OR
17            a.txt1 IS NULL AND a.txt2=b.txt2 OR
18            Nvl(a.txt2, a.txt1) IS NULL AND a.txt3 = b.txt3 OR
19            Nvl(a.txt2, a.txt1) IS NULL  AND a.txt3 IS NULL AND a.txt4 = b.txt4);
       PID TXT1   TXT2   TXT3   TXT4
       111 test   pak    ced    su
       222 null   pak    ced2   su2
       333 null   null   ced3   su3
       444 null   null   null   su3
null       text5  null   null   su3
null       null   null   null   nullJohn