SYS_CONNECT_BY_PATH is valid only in hierarchical queries(级联查询). It returns the path of a column value from root to node, with column values separated by char for each row returned by CONNECT BY condition.
Both column and char can be any of the data types CHAR, VARCHAR2, NCHAR, or NVARCHAR2. The string returned is of VARCHAR2 data type and is in the same character set as column.
See Also:"Hierarchical Queries" for more information about hierarchical queries and CONNECT BY conditions
The following example returns the path of employee names from employee Kochhar to all employees of Kochhar (and their employees):
SELECT LPAD(' ', 2*level-1)||SYS_CONNECT_BY_PATH(last_name, '/') "Path" FROM employees START WITH last_name = 'Kochhar' CONNECT BY PRIOR employee_id = manager_id; Path ------------------------------ /Kochhar/Greenberg/Chen /Kochhar/Greenberg/Faviet /Kochhar/Greenberg/Popp /Kochhar/Greenberg/Sciarra /Kochhar/Greenberg/Urman /Kochhar/Higgins/Gietz /Kochhar/Baer /Kochhar/Greenberg /Kochhar/Higgins /Kochhar/Mavris /Kochhar/Whalen /Kochhar第一个参数是 形成树形式的字段，
START WITH ename = 'KING'
CONNECT BY PRIOR empno = mgr;