CASE Statement - and checking number ranges

Question

I am attempting to write a bit of SQL that can be used to do a count of Requisition Values, in different value bands, e.g.:
0 - 250
251 - 500
501 - 1000
etc...
I have got this far:
SELECT   sum_value
       , COUNT(req_id) req_ct
    FROM (SELECT   prha.requisition_header_id req_id
                 , CASE SUM(prla.unit_price * prla.quantity)
                      WHEN 250
                         THEN '250'
                      WHEN 500
                         THEN '500'
                      WHEN 500
                         THEN '1000'
                      ELSE 'OTHER'
                   END sum_value
              FROM po.po_requisition_headers_all prha
                 , po.po_requisition_lines_all prla
             WHERE prha.requisition_header_id = prla.requisition_header_id
               AND prha.creation_date >= SYSDATE - 3
          GROUP BY prha.requisition_header_id
                 , prla.requisition_header_id) rt
GROUP BY sum_value;
SUM_V     REQ_CT
250            3
500            6
OTHER        726But - it is not that great, in that it counts REQs with an exact value of 250,400,500 etc.
I am trying to work out the syntax to allow the CASE statement to work with ranges, but I can't work it out.
I have naively attempted this, for example:
WHEN > 250 AND 500
But that errors out, because I can see that the '>' needs to know what it is checking
Any help much appreciated.
Thank you

Answer 1

Thanks for the reply Sarma,
I've attempted that:
SELECT   sum_value
       , COUNT(req_id) req_ct
    FROM (SELECT   prha.requisition_header_id req_id
                 , CASE SUM(prla.unit_price * prla.quantity)
                      WHEN BETWEEN 250 AND 500
                         THEN '250 - 500'
                      WHEN BETWEEN 501 AND 1000
                         THEN '501 - 1000'
                      WHEN BETWEEN 1001 AND 2500
                         THEN '1001 - 2500'
                      ELSE 'OTHER'
                   END sum_value
              FROM po.po_requisition_headers_all prha
                 , po.po_requisition_lines_all prla
             WHERE prha.requisition_header_id = prla.requisition_header_id
               AND prha.creation_date >= SYSDATE - 3
          GROUP BY prha.requisition_header_id
                 , prla.requisition_header_id) rt
GROUP BY sum_value;But I can see that it doesn't work because I need to state what 'blah' is!
For example, if I tried to state 'blah' as follows:
SELECT   sum_value
       , COUNT(req_id) req_ct
    FROM (SELECT   prha.requisition_header_id req_id
                 , CASE SUM(prla.unit_price * prla.quantity)
                      WHEN SUM(prla.unit_price * prla.quantity) BETWEEN 250 AND 500
                         THEN '250 - 500'
                      WHEN SUM(prla.unit_price * prla.quantity) BETWEEN 501 AND 1000
                         THEN '501 - 1000'
                      WHEN SUM(prla.unit_price * prla.quantity) BETWEEN 1001 AND 2500
                         THEN '1001 - 2500'
                      ELSE 'OTHER'
                   END sum_value
              FROM po.po_requisition_headers_all prha
                 , po.po_requisition_lines_all prla
             WHERE prha.requisition_header_id = prla.requisition_header_id
               AND prha.creation_date >= SYSDATE - 3
          GROUP BY prha.requisition_header_id
                 , prla.requisition_header_id) rt
GROUP BY sum_value;It still errors. I guess I am doing something fundamentally wrong, but I can't see how I can refer to the 'sum' value, to then use it in the Between section of the Case statement.
Thanks