Return results for one column value but not another SQL

Question

I have the two tables below:

I want to list all items that have been selected for event 2099 but NOT for event 2201. How would I do this?

I have this:

SELECT ITEMNO, UNIT_PRICE, EST_SERVINGS                                
FROM MENUITEM                                                          
WHERE ITEMNO IN (SELECT ITEMNO FROM SELECTEDITEM WHERE EVENTID = 2099);

but this only returns the itemno's with event 2099. The answer should just be 520.

Answer 1

I am a fan of using aggregation with a having clause for this type of query.

SELECT mi.ITEMNO, mi.UNIT_PRICE, mi.EST_SERVINGS                                
FROM MENUITEM mi JOIN
     SELECTEDITEM si
     ON mi.ITEMNO = si.ITEMNO
GROUP BY mi.ITEMNO, mi.UNIT_PRICE, mi.EST_SERVINGS 
HAVING SUM(CASE WHEN EVENTID = 2099 THEN 1 ELSE 0 END) > 0 AND
       SUM(CASE WHEN EVENTID = 2201 THEN 1 ELSE 0 END) = 0;

Each condition in the having clause is counting the number of times that a particular item is used for an event. The > 0 means the item is used at least once. The = 0 means the item does not appear. So the first says that the item was used for event 2099 and the second that the item was not used for 2202.

I like this method of expressing these "set-within-sets" queries because it is very flexible. If you want to say that event 2101 should be included, just add another clause:

HAVING SUM(CASE WHEN EVENTID = 2099 THEN 1 ELSE 0 END) > 0 AND
       SUM(CASE WHEN EVENTID = 2101 THEN 1 ELSE 0 END) > 0 AND
       SUM(CASE WHEN EVENTID = 2201 THEN 1 ELSE 0 END) = 0;

Answer 2

Try this:

SELECT ITEMNO, UNIT_PRICE, EST_SERVINGS                                
FROM MENUITEM MI                             
WHERE
EXISTS
    (SELECT 'ON2099'
    FROM SELECTEDITEM SI
    WHERE SI.ITEMNO = MI.ITEMNO AND SI.EVENTID = 2099)
AND NOT EXISTS
    (SELECT 'ON2201'
    FROM SELECTEDITEM SI
    WHERE SI.ITEMNO = MI.ITEMNO AND SI.EVENTID = 2201)