sql - How to use Union or Intersect instead of an OR in my Join -


the query below works, i've read, or in join not efficient way results. think maybe should using union or intersect, can't figure out how accomplish that. can explain 'proper' results?

with cte1 (select sc, sn, count(al) unexcused                att                al = 'u'                group sc, sn),      cte2 (select sc, sn, count(al) suspended                att                al = 's'                group sc, sn)  select stu.id, stu.sc, stu.sn,         isnull(cte1.unexcused, '') unx,        isnull(cte2.suspended, '') sus  cte2 full join cte1         on cte1.sc = cte2.sc            , cte1.sn = cte2.sn join stu    on (cte1.sc = stu.sc        , cte1.sn = stu.sn)       or (cte2.sc = stu.sc           , cte2.sn = stu.sn) stu.sc in (1,2,4,9,11,15)

this sample of output:

id      sc  sn     unx  sus 4291432 15  602    0    8 4296250 15  688    6    3 4216462 15  695    0    12 4916602 15  623    0    2 4295193 1   150    1    0 4215874 2   216    1    0 4005707 15  297    1    0

thank you.

personally, i'd change query around this:

with cte1 (select sc, sn, count(al) unexcused                att                al = 'u'                group sc, sn),      cte2 (select sc, sn, count(al) suspended                att                al = 's'                group sc, sn)  select stu.id, stu.sc, stu.sn,         isnull(cte1.unexcused, '') unx,        isnull(cte2.suspended, '') sus  stu left join cte1        on (cte1.sc = stu.sc             , cte1.sn = stu.sn)  left join cte2         on (cte2.sc = stu.sc             , cte2.sn = stu.sn) stu.sc in (1,2,4,9,11,15)

.... if no other reason makes intended results little more clear. note optimizer may still generate same explain plan.


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