Note: To detect a cycle, only the results returned by the iterative SELECT statement are checked. 注意:要检测循环,在检测循环时,系统只会检查迭代select语句返回的结果。
The result of the current iterative select statement is merged with the result of the initial select statement and all results returned by the previous iterations using a UNION ALL clause. 使用UNIONALL子句,可将当前的迭代SELECT语句的结果与初始SELECT语句的结果以及之前的迭代返回的所有结果合并在一起。