尝试获取ORACLE的工作日列表时得到ORA-00904

In my projet I need to use a function called getWorkingDay(beg_date Date,slider Integer). This function is used to find the n-th last working day from the date beg_date (where "n" is the value from slider). What I would like to do is to get all of the working days within a date range defined by beg_date and end_date. I would like to use a SELECT statement and the function above to get the working days list. I tried this statement with beg_date=sysdate-45 and end_date=sysdate :

SELECT * FROM(
SELECT getworkingDay(sysdate,slide) dt FROM DUAL
WHERE slide>0 and slide<=sysdate-(sysdate-45))
WHERE dt >=sysdate-45

我收到以下错误：

ORA-00904：“幻灯片”：无效的标识符

您能帮我找到解决这个问题的方法吗？