ALTER VIEW Statement
Changes the characteristics of a view. The syntax has two forms:
- The AS clause associates the view with a different query.
- The RENAME TO clause changes the name of the view, moves the view to a different database, or both.
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
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 Query Option for details.
Cancellation: Cannot be cancelled.
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
Related information:
Overview of Impala Views, CREATE VIEW Statement, DROP VIEW Statement