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Hive >> mail # user >> Combine two overlapping schema?


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Keith Wiley 2013-03-06, 18:03
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Re: Combine two overlapping schema?
Of the top of my head, I think UNION ALL should work if you explicitly
project out the missing columns with NULL or other values, e.g. using
nested SELECTs, something like

SELECT * FROM (
 SELECT a,b,c, Y, NULL AS Z FROM table1
 UNION ALL
 SELECT a,b,c, NULL AS Y, Z FROM table2
) table12;

On Wed, Mar 6, 2013 at 12:03 PM, Keith Wiley <[EMAIL PROTECTED]> wrote:

> I have two tables which have overlapping but nonidentical schema.  I want
> to creating a new table that unions them, leaving nulls in any given row
> where a column name doesn't occur in the other table:
>
> SCHEMA 1: { a, b, c, Y }
> row:      { 1, 2, 3, 4 }
>
> SCHEMA 2: { a, b, c, Z }
> row:      { 5, 6, 7, 8 }
>
> NEW SCHEMA: { a, b, c, Y, Z }
> new row:  { a:1, b:2, c:3, Y:4, Z:null }
> new row:  { a:5, b:6, c:7, Y:null, Z:8 }
>
> I don't think either "full outer join" or "union all" works.  I'm not sure
> how to do this.  Any ideas?
>
> Thanks.
>
>
> ________________________________________________________________________________
> Keith Wiley     [EMAIL PROTECTED]     keithwiley.com
> music.keithwiley.com
>
> "You can scratch an itch, but you can't itch a scratch. Furthermore, an
> itch can
> itch but a scratch can't scratch. Finally, a scratch can itch, but an itch
> can't
> scratch. All together this implies: He scratched the itch from the scratch
> that
> itched but would never itch the scratch from the itch that scratched."
>                                            --  Keith Wiley
>
> ________________________________________________________________________________
>
>
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Keith Wiley 2013-03-06, 18:44