ALTER
VIEW Statement
Replaces a view definition with a modified version.
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 }
- 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.
- 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 IQ currently ignores this option (it supports the syntax for compatibility reasons).
- obfuscate the definition of the view and cause
the view to become hidden from view, for example in
SAP IQ Cockpit. Explicit references to the view
still work.CautionWhen 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.
The SET HIDDEN operation is irreversible.
- 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 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 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.
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.
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.
- 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.
- SQL—Vendor extension to ISO/ANSI SQL grammar.
- SAP Database products—Not supported by SAP ASE.