CAN I BREAK A BRANCH IN CONNECT BY

Question

Hi:
Suppose I have the following CONNECT BY query:
SELECT  FIELD1, FIELD2, LEVEL
FROM    A_TABLE
CONNECT BY PRIOR FIELD2 = FIELD1
START   WITH FIELD1     = 2
ORDER   BY FIELD1, FIELD2
/here is the table and data:
CREATE TABLE A_TABLE
  FIELD1  NUMBER,
  FIELD2 NUMBER
INSERT INTO A_TABLE VALUES(2, 4);
INSERT INTO A_TABLE VALUES(2, 8);
INSERT INTO A_TABLE VALUES(2, 12);
INSERT INTO A_TABLE VALUES(2, 16);
INSERT INTO A_TABLE VALUES(4, 5);
INSERT INTO A_TABLE VALUES(4, 7);
INSERT INTO A_TABLE VALUES(8, 9);
INSERT INTO A_TABLE VALUES(8, 11);
INSERT INTO A_TABLE VALUES(12, 13);
INSERT INTO A_TABLE VALUES(12, 16);The query produces:
    FIELD1     FIELD2      LEVEL
         2          4          1
         2          8          1
         2         12          1
         2         16          1
         4          5          2
         4          7          2
         8          9          2
         8         11          2
        12         13          2
        12         15          2Which in a branch display would be
  2
  |
  |--4
  |  |
  |  |--5
  |  |
  |  |--7
  |
  |--8
  |  |
  |  |--9
  |  |
  |  |--11
  |
  |
  |--12
  |  |
  |  |--13
  |  |
  |  |--15
  |
  |--16Suppose that when I issue this query, because 4 relates to some criteria that says not to show 4 or anything below it, is there any syntax I can use in the connect by to make skip the branch that starts at 4 and includes 5 and 7. Or do I write my query as follows?
SELECT  FIELD1, FIELD2, LEVEL
FROM    A_TABLE
WHERE   FIELD1 <> 4
AND     FIELD2 <> 4
CONNECT BY PRIOR FIELD2 = FIELD1
START   WITH FIELD1     = 2
ORDER   BY FIELD1, FIELD2
/Thanks for any help,
Thomas

Answer 1

select field1, field2, level
  from a_table
where field2 <> 4
connect by prior field2 = field1 and field1 <> 4
start with field1 = 2
  order by field1, field2;will prevent the branch into leaf 4 altogether (as opposed to branching and then having to filter later, which gets interesting if 4 has any grandchildren).
The field2 filter is still necessary to filter out the row that shows 4 as a child of 2.