ALTER VIEW Statement

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Syntax

Syntax 1 – Alter the structure of the view

ALTER VIEW
   … [ owner.]view-name [ ( column-name [ , … ] ) ]
   … AS select-statement
   … [ WITH CHECK OPTION ]

Syntax 2 – Change attributes for the view

ALTER VIEW
   … [ owner.]view-name 
   … { SET HIDDEN | RECOMPILE | DISABLE | ENABLE }

Parameters

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AS – the SELECT statement on which the view is based must not contain an ORDER BY clause, a subquery in the SELECT list, or a TOP or FIRST qualification. It may have a GROUP BY clause and may be a UNION.

WITH CHECK OPTION – rejects any updates and inserts to the view that do not meet the criteria of the views as defined by its SELECT statement. However, SAP Sybase IQ currently ignores this option (it supports the syntax for compatibility reasons).

SET HIDDEN – obfuscate the definition of the view and cause the view to become hidden from view, for example in SAP Control Center. Explicit references to the view still work.
Warning! The SET HIDDEN operation is irreversible.
When you use SET HIDDEN, you can unload and reload the view into other databases. Debugging using the debugger does not show the view definition, nor is it available through procedure profiling. If you need to change the definition of a hidden view, you must drop the view and create it again using the CREATE VIEW statement.

RECOMPILE – recreate the column definitions for the view. Identical in functionality to the ENABLE clause, except you can use it on a view that is not disabled.

DISABLE – disable the view from use by the database server.
When you use the DISABLE clause, the view is no longer available for use by the database server to answer queries. Disabling a view is similar to dropping one, except that the view definition remains in the database. Disabling a view also disables any dependent views. Therefore, the DISABLE clause requires exclusive access, not only to the view being disabled, but to any dependent views, which are also disabled.

ENABLE – enable a disabled view, which causes the database server to recreate the column definitions for the view. Before you enable a view, you must enable any views on which it depends.

Usage

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When you alter a view, existing permissions on the view are maintained and do not require reassignment. Instead of using the ALTER VIEW statement, you could also drop the view and recreate it using DROP VIEW and CREATE VIEW, respectively. If you do this, view permissions must be reassigned.

After completing the view alteration using Syntax 1, the database server recompiles the view. Depending on the type of change you made, if there are dependent views, the database server attempts to recompile them. If you made changes that impact a dependent view, that view may become invalid, requiring you to alter the definition for the dependent view.

Warning! If the SELECT statement defining the view contains an asterisk (*), the number of the columns in the view could change if columns were added or deleted from the underlying tables. The names and data types of the view columns could also change.

Altering the structure of a view requires that you replace the entire view definition with a new definition, much as you would when creating the view using the CREATE VIEW statement.

Side effects:

Automatic commit
All procedures and triggers are unloaded from memory, so that any procedure or trigger that references the view reflects the new view definition. The unloading and loading of procedures and triggers can have a performance impact if you regularly alter views.

Standards

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SQL—Vendor extension to ISO/ANSI SQL grammar.
SAP Sybase Database product—Not supported by Adaptive Server.

Permissions

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RECOMPILE or ENABLE clause – For view requires one of:

ALTER ANY VIEW system privilege.
ALTER ANY OBJECT system privilege.
You own the view.
Also require one of:
- SELECT ANY TABLE system privilege.
- SELECT privilege on the underlying tables of the view.

For materialized view requires one of:

ALTER ANY MATERIALNESS VIEW system privilege.
ALTER ANY OBJECT system privilege.
You own the materialized view.
Also require one of:
- SELECT ANY TABLE system privilege.
- SELECT privilege on the underlying tables of the materialized view.

DISABLE clause – For view requires one of:

ALTER ANY VIEW system privilege.
ALTER ANY OBJECT system privilege.
You own the view.

For materialized view requires one of:

ALTER ANY MATERIALIZED VIEW system privilege.
ALTER ANY OBJECT system privilege.
You own the materialized view.

All other clauses require one of:

ALTER ANY OBJECT system privilege.
You own the view.