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Hive / SQL select last item from values separated by commas

Posted on 2013-10-30
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Last Modified: 2013-11-04
I've got a field that holds values separated by commas.  How can i get the *LAST* value from the list?

---------------------------
|    Example_Field   |
---------------------------
[apple, orange, pear]
[apple, pear]    
[pear, pear, apple]
[orange]
---------------------------

I want a select query to return the last value from each list:
pear
pear
apple
orange

So:
Select SpecialFunctionToGetLastVal(Example_Field) as LastFruit from Table

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This is for a hive query, but i'll cross that bridge when i come to it.  Is there some generic function or method in SQL to do this?

Thanks in advance
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Question by:ducky801
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5 Comments
 
LVL 41

Accepted Solution

by:
Kyle Abrahams earned 2000 total points
ID: 39612513
this should do it for you:

select substring(
                          Example_Field,
                                    len(Example_Field) - charindex(',', reverse(Example_Field)) + 2,
                                    charindex(',', reverse(Example_Field)))


note that if your values are seperated by the ', ' then you would use a ' ' instead of ',' in the query (2 replacements).
0
 
LVL 29

Expert Comment

by:sammySeltzer
ID: 39612516
Sorry this is wrong. - my first solution  that is.

How about this?

DECLARE @LastVAR NVARCHAR(100)
DECLARE MYTESTCURSOR CURSOR
DYNAMIC 
FOR
SELECT Example_Field as lastItem FROM yourtable
OPEN MYTESTCURSOR
FETCH LAST FROM MYTESTCURSOR INTO @LastVAR 
CLOSE MYTESTCURSOR
DEALLOCATE MYTESTCURSOR
SELECT @LastVAR 

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OR

set rowcount 1
 
select * from yourtable order by id desc

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0
 
LVL 32

Expert Comment

by:awking00
ID: 39614755
I'm not very familiar with Hive, but I do know it has string functions for reverse(), instr(), trim(), replace(), and substr() from which you could create a user_defined function. In pseudo code, something like the following:
if instr(field,',') = 0 then field
else
reverse(field)
find first position of reversed field using instr(reverse(field),',')
substr(reverse(field),1, instr(reverse(field),',')
replace the ',' from above, then trim the result
and finally reverse that.
Sorry I couldn't be more specific but I hope this might help.
0
 
LVL 41

Expert Comment

by:Sharath
ID: 39618478
Is it a STRING or ARRAY data type? And do you have open and closing brackets also as part of the string?
0
 
LVL 41

Expert Comment

by:Sharath
ID: 39618482
try this.

SELECT reverse(sentences(reverse(your_column))[0][0]) FROM your_table

tested on my machine and it returned the last element.

select reverse(sentences(reverse('abc,def,ghi'))[0][0]) from default.dual
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