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From "Ratner, Alan S (IS)" <>
Subject Group By Concatenation
Date Thu, 01 Nov 2012 18:27:18 GMT
Sorry to ask what is probably a very naïve Hive question but here goes:

I have a table as follows:
Col1   Col2
K1       V1
K1       V1
K2       V1
K3       V1
K1       V2
K1       V3
K2       V2

Now I have managed to SELECT Col1,COUNT(DISTINCT Col2) FROM ... BY COL1; to obtain
K1       3
K2       2
K3       1

But what I want is a concatenated list of all the distinct Col2 values for each Col1 key.
K1       V1       V2       V3
K2       V1       V2
K3       V1

This is something absolutely trivial in MR but I cannot seem to find anything in Hive that
will do this for me.  Do I have to write a UDF to accomplish this?


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