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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hive/LanguageManual/LanguageManual/SubQueries" by RaghothamMurthy
Date Wed, 21 Jan 2009 23:33:23 GMT
Dear Wiki user,

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The following page has been changed by RaghothamMurthy:
http://wiki.apache.org/hadoop/Hive/LanguageManual/LanguageManual/SubQueries

------------------------------------------------------------------------------
+ deleted
- Syntax:
- {{{
- SELECT ... FROM (subquery) name ...
- }}}
- Hive supports subqueries only in the FROM clause. The subquery has to be given a name because
every table in a FROM clause must have a name. Columns in the subquery select list must have
unique names. The columns in the subquery select list are available in the outer query just
like columns of a table. The subquery can also be a query expression with UNION. Hive supports
arbitrary levels of sub-queries.
  
- Example with simple subquery:
- {{{
- SELECT col 
- FROM (
-   SELECT a+b AS col
-   FROM t1
- ) t2
- }}}
- 
- Example with subquery containing a UNION ALL:
- {{{
- SELECT t3.col
- FROM (
-   SELECT a+b AS col
-   FROM t1
-   UNION ALL
-   SELECT c+d AS col
-   FROM t2
- ) t3
- }}}
- 

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