whats is wrong with this query.
I need to get all hours of the 24 hours period to count hits per hour.
I want to make a case when 0-24 but I can not do the first work

```
SELECT
    (
    CASE WHEN (
           CAST(TO_CHAR(dg_user_acess.dt_user_acess, 'HH24') >= '00')
         AND
          CAST(TO_CHAR(dg_user_acess.dt_user_acess, 'HH24') < '01')
         )
        THEN ('00:00 as 01:00')
        ELSE '0' END
    ) as hour,        
    count(*)
FROM dg_user_acess
GROUP by hour

```

i get the error

Erro de SQL: ORA-00905: palavra-chave não encontrada
00905. 00000 - "missing keyword"

the table data is like this

```
pk| dt_user_acess
01| 2014-10-21 08:30:12
02| 2014-10-21 08:40:27
03| 2014-10-21 08:56:18
04| 2014-10-21 09:15:19
05| 2014-10-21 10:42:48
...

```

and the result I would like something like this (not write the case when all schedulesin query to not pollute the code)

```
'00:00 as 01:00' 0
'01:00 as 02:00' 0
'02:00 as 03:00' 0
'03:00 as 04:00' 0
'04:00 as 05:00' 0
'05:00 as 06:00' 0
'06:00 as 07:00' 0
'07:00 as 08:00' 0
'08:00 as 09:00' 3
'09:00 as 10:00' 1
'10:00 as 11:00' 1
'11:00 as 12:00' 0
'12:00 as 13:00' 0 
'13:00 as 14:00' 0 
'14:00 as 15:00' 0 
'15:00 as 16:00' 0 
'16:00 as 17:00' 0 
'17:00 as 18:00' 0 
'18:00 as 19:00' 0 
'19:00 as 20:00' 0 
'20:00 as 21:00' 0 
'21:00 as 22:00' 0 
'22:00 as 23:00' 0 
'23:00 as 23:59' 0 

```