From the Oracle documentation:
To find the children of a parent row, Oracle evaluates the PRIOR expression of the CONNECT BY condition for the parent row and the other expression for each row in the table. Rows for which the condition is true are the children of the parent. The CONNECT BY condition can contain other conditions to further filter the rows selected by the query.
When Oracle select child node for a parent node, it selects from all rows except the current row right? Can a row appear multi times in the result set (I mean a row is both the child node of row A and row B)?