All this pseudocolumn does is to return 1 if a given row is a leaf in recursion.
这个伪列只是当一个给定行在递归中是叶子的时候返回1。
2
The pseudocolumn LEVEL is used in a string to make the hierarchy visible.
可在字符串中使用伪列LEVEL，使分层结构变得可视。
3
Unless Oracle has introduced yet another pseudocolumn or keywords that I'm not aware of, all of Oracle's recursive features have now been mapped to DB2 UDB for Linux, UNIX, and Windows.
除非oracle引入了我不知道的其他伪列或关键字，否则Oracle所有的递归特性现在都被映射到DB 2 UDB for Linux、UNIX和Windows。