I'm trying to find the avg start time for a date range but the avg function doesn't seem to work on `to_char(cast(Start_Dt as date),'HH24:MI')` (Start\_Dt sample: `12/12/18 02:30:13`). Any ideas on how I can get my desired result?

sample:

```
SELECT
job_nm
avg(to_char(cast(Start_Dt as date),'HH24:MI'))
FROM batch_table
Where Start_Dt >= trunc(sysdate-10)
group by job_nm

```

> 
> Error: ORA-01722: invalid number
>  01722. 00000 - "invalid number"
>  \*Cause: The specified number was invalid.
>  \*Action: Specify a valid number.
> 
> 
> 

Ideal results would be 
the query only looks at jobs ran in the last 10 days and the average start time for the period.

desired results:

```
 JOB_NM | AVG Time
    open   |  2:30
    close  |  3:30

```