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 VijendarGanta: http://wiki.apache.org/hadoop/Hive/Tutorial ------------------------------------------------------------------------------ == Language capabilities == Hive query language provides the basic SQL like operations. These operations work on tables or partitions. These operations are: - * Ability to filter rows from a table using a where clause. + * Ability to filter rows from a table using a where clause. - * Ability to select certain columns from the table using a select clause. + * Ability to select certain columns from the table using a select clause. - * Ability to do equi-joins between two tables. + * Ability to do equi-joins between two tables. - * Ability to evaluate aggregations on multiple "group by" columns for the data stored in a table. + * Ability to evaluate aggregations on multiple "group by" columns for the data stored in a table. - * Ability to store the results of a query into another table. + * Ability to store the results of a query into another table. - * Ability to download the contents of a table to a local (e.g., nfs) directory. + * Ability to download the contents of a table to a local (e.g., nfs) directory. - * Ability to store the results of a query in a hadoop dfs directory. + * Ability to store the results of a query in a hadoop dfs directory. - * Ability to manage tables and partitions (create, drop and alter). + * Ability to manage tables and partitions (create, drop and alter). - * Ability to plug in custom scripts in the language of choice for custom map/reduce jobs. + * Ability to plug in custom scripts in the language of choice for custom map/reduce jobs. = Usage and Examples = The following examples highlight some salient features of the system. A detailed set of query test cases can be found at [http://svn.apache.org/viewvc/hadoop/hive/trunk/ql/src/test/queries/clientpositive/ Hive Query Test Cases] and the corresponding results can be found at [http://svn.apache.org/viewvc/hadoop/hive/trunk/ql/src/test/results/clientpositive/ Query Test Case Results] @@ -183, +183 @@ == Creating Tables == An example statement that would create the page_view table mentioned above would be like: {{{ - CREATE TABLE page_view(viewTime INT, userid BIGINT, page_url STRING, referrer_url STRING, ip STRING COMMENT 'IP Address of the User') @@ -212, +211 @@ It is also a good idea to bucket the tables on certain columns so that efficient sampling queries can be executed against the data set (note: If bucketing is absent, random sampling can still be done on the table). The following example illustrates the case of the page_view table which is bucketed on userid column: {{{ CREATE TABLE page_view(viewTime INT, userid BIGINT, - page_url STRING, referrer_url STRING, ip STRING COMMENT 'IP Address of the User') COMMENT 'This is the page view table'
