hadoop-common-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "Hive/LanguageManual/Select" by RaghothamMurthy
Date Thu, 22 Jan 2009 01:50:09 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

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

------------------------------------------------------------------------------
  ]
  [LIMIT number]
  }}}
-  * A SELECT statement can be part of a [wiki:Self:Hive/LanguageManual/Union union] query
or a [wiki:Self:Hive/LanguageManual/SubQuery subquery] of another query.
+  * A SELECT statement can be part of a [wiki:Self:Hive/LanguageManual/Union union] query
or a [wiki:Self:Hive/LanguageManual/SubQueries subquery] of another query.
-  * table_reference indicates the input to the query. It can be a regular table, a [wiki:Self:Hive/LanguageManual/Joins
join construct] or a [wiki:Self:Hive/LanguageManual/SubQuery subquery].
+  * table_reference indicates the input to the query. It can be a regular table, a [wiki:Self:Hive/LanguageManual/Joins
join construct] or a [wiki:Self:Hive/LanguageManual/SubQueries subquery].
   * Simple query. For example, the following query retrieves all columns and all rows from
table t1.
  {{{
  SELECT * FROM t1
@@ -39, +39 @@

      2
  }}}
  
-  * Partition based queries. In general, a SELECT query scans the entire table (other than
for [wiki:Self:Hive/LanguageManual/Sampling sampling]). If a table created using the [wiki:Self:Hive/LanguageManual/DDL
PARTITIONED BY] clause, a query can do '''input pruning''' and scan only a fraction of the
table relevant to the query. For example, if table page_views is partitioned on column date,
the following query retrieves rows for just one day 2008-03-31.
+  * Partition based queries. In general, a SELECT query scans the entire table (other than
for [wiki:Self:Hive/LanguageManual/Sampling sampling]). If a table created using the [wiki:Self:Hive/LanguageManual/DDL
PARTITIONED BY] clause, a query can do '''input pruning''' and scan only a fraction of the
table relevant to the query. Hive currently does input pruning only if the partition predicates
are specified in the WHERE clause closest to the table_reference in the FROM clause. For example,
if table page_views is partitioned on column date, the following query retrieves rows for
just one day 2008-03-31.
  {{{
      SELECT page_views.* 
      FROM page_views 

Mime
View raw message