This is the documentation for CDH 5.0.x. Documentation for other versions is available at Cloudera Documentation.

ALTER VIEW Statement

Changes the query associated with a view, or the associated database and/or name of the view.

Because a view is purely a logical construct (an alias for a query) with no physical data behind it, ALTER VIEW only involves changes to metadata in the metastore database, not any data files in HDFS.

Syntax:

ALTER VIEW [database_name.]view_name AS select_statement
ALTER VIEW [database_name.]view_name RENAME TO [database_name.]view_name

Statement type: DDL

Related information:

Views, CREATE VIEW Statement, DROP VIEW Statement

If you connect to different Impala nodes within an impala-shell session for load-balancing purposes, you can enable the SYNC_DDL query option to make each DDL statement wait before returning, until the new or changed metadata has been received by all the Impala nodes. See SYNC_DDL for details.

Examples:

create table t1 (x int, y int, s string);
create table t2 like t1;
create view v1 as select * from t1;
alter view v1 as select * from t2;
alter view v1 as select x, upper(s) s from t2;

To see the definition of a view, issue a DESCRIBE FORMATTED statement, which shows the query from the original CREATE VIEW statement:

[localhost:21000] > create view v1 as select * from t1;
[localhost:21000] > describe formatted v1;
Query finished, fetching results ...
+------------------------------+------------------------------+----------------------+
| name                         | type                         | comment              |
+------------------------------+------------------------------+----------------------+
| # col_name                   | data_type                    | comment              |
|                              | NULL                         | NULL                 |
| x                            | int                          | None                 |
| y                            | int                          | None                 |
| s                            | string                       | None                 |
|                              | NULL                         | NULL                 |
| # Detailed Table Information | NULL                         | NULL                 |
| Database:                    | views                        | NULL                 |
| Owner:                       | cloudera                     | NULL                 |
| CreateTime:                  | Mon Jul 08 15:56:27 EDT 2013 | NULL                 |
| LastAccessTime:              | UNKNOWN                      | NULL                 |
| Protect Mode:                | None                         | NULL                 |
| Retention:                   | 0                            | NULL                 |
| Table Type:                  | VIRTUAL_VIEW                 | NULL                 |
| Table Parameters:            | NULL                         | NULL                 |
|                              | transient_lastDdlTime        | 1373313387           |
|                              | NULL                         | NULL                 |
| # Storage Information        | NULL                         | NULL                 |
| SerDe Library:               | null                         | NULL                 |
| InputFormat:                 | null                         | NULL                 |
| OutputFormat:                | null                         | NULL                 |
| Compressed:                  | No                           | NULL                 |
| Num Buckets:                 | 0                            | NULL                 |
| Bucket Columns:              | []                           | NULL                 |
| Sort Columns:                | []                           | NULL                 |
|                              | NULL                         | NULL                 |
| # View Information           | NULL                         | NULL                 |
| View Original Text:          | SELECT * FROM t1             | NULL                 |
| View Expanded Text:          | SELECT * FROM t1             | NULL                 |
+------------------------------+------------------------------+----------------------+
Returned 29 row(s) in 0.05s

Page generated September 3, 2015.