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Alan Gates commented on HIVE-6100:
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INTERSECT, UNION, and EXCEPT are all SQL constructs. Hive implements UNION ALL (only under very limited circumstances). I'm saying if you are going to add these to Hive (and I agree they should be added) why not add them as part of the language itself, which is how most SQL users will expect them to be, rather than bolting them on with a UDF.
> Introduce basic set operations as UDFs
> --------------------------------------
>
> Key: HIVE-6100
> URL: https://issues.apache.org/jira/browse/HIVE-6100
> Project: Hive
> Issue Type: New Feature
> Components: UDF
> Reporter: Kostiantyn Kudriavtsev
> Priority: Minor
> Fix For: 0.13.0
>
>
> Introduce basic set operations:
> 1. Intersection: The intersection of A and B, denoted by A ∩ B, is the set of all things that are members of both A and B.
> select set_intersection(arr_a, arr_b) from dual
> 2. Union: The union of A and B, denoted by A ∪ B, is the set of all things that are members of either A or B.
> select set_union(arr_a, arr_b) from dual
> 3. Symmetric difference: the symmetric difference of two sets is the set of elements which are in either of the sets and not in their intersection.
> select set_symdiff(arr_a, arr_b) from dual
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