Question

I am working on a query for a report in Oracle 10g.

I need to generate a short list of each course along with the number of times they were offered in the past year (including ones that weren’t actually offered).

I created one query

SELECT coursenumber, count(datestart) AS Offered
FROM class
WHERE datestart BETWEEN (sysdate-365) AND sysdate
GROUP BY coursenumber;

Which produces

COURSENUMBER    OFFERED
----           ----------
ST03              2
PD01              1
AY03              2
TB01              4

This query is all correct. However ideally I want it to list those along with COURSENUMBER HY and CS in the left column as well with 0 or null as the OFFERED value. I have a feeling this involves a join of sorts, but so far what I have tried doesn’t produce the classes with nothing offered.

The table normally looks like

REFERENCE_NO DATESTART TIME TIME        EID     ROOMID COURSENUMBER
------------ --------- ---- ---- ---------- ---------- ----
         256 03-MAR-11 0930 1100          2          2 PD01
         257 03-MAY-11 0930 1100         12          7 PD01
         258 18-MAY-11 1230 0100         12          7 PD01
         259 24-OCT-11 1930 2015          6          2 CS01
         260 17-JUN-11 1130 1300          6          4 CS01
         261 25-MAY-11 1900 2000         13          6 HY01
         262 25-MAY-11 1900 2000         13          6 HY01
         263 04-APR-11 0930 1100         13          5 ST03
         264 13-SEP-11 1930 2100          6          4 ST03
         265 05-NOV-11 1930 2100          6          5 ST03
         266 04-FEB-11 1430 1600          6          5 ST03
         267 02-JAN-11 0630 0700         13          1 TB01
         268 01-FEB-11 0630 0700         13          1 TB01
         269 01-MAR-11 0630 0700         13          1 TB01
         270 01-APR-11 0630 0700         13          1 TB01
         271 01-MAY-11 0630 0700         13          1 TB01
         272 14-MAR-11 0830 0915          4          3 AY03
         273 19-APR-11 0930 1015          4          3 AY03
         274 17-JUN-11 0830 0915         14          3 AY03
         275 14-AUG-09 0930 1015         14          3 AY03
         276 03-MAY-09 0830 0915         14          3 AY03

Answer 1

I think something like this should work for you, by just doing it as a subquery.

SELECT distinct c.coursenumber, 
       (SELECT COUNT(*)
        FROM class
        WHERE class.coursenumber = c.coursenumber
          AND datestart BETWEEN (sysdate-365) AND sysdate
        ) AS Offered
FROM class c