# `ALTER VIEW`
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The `ALTER VIEW` statement allows changing various properties of an existing view, and Aurora DSQL supports all the PostgreSQL syntax for this command.

## Supported syntax
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```
ALTER VIEW [ IF EXISTS ] name ALTER [ COLUMN ] column_name SET DEFAULT expression
ALTER VIEW [ IF EXISTS ] name ALTER [ COLUMN ] column_name DROP DEFAULT
ALTER VIEW [ IF EXISTS ] name OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER VIEW [ IF EXISTS ] name RENAME [ COLUMN ] column_name TO new_column_name
ALTER VIEW [ IF EXISTS ] name RENAME TO new_name
ALTER VIEW [ IF EXISTS ] name SET SCHEMA new_schema
ALTER VIEW [ IF EXISTS ] name SET ( view_option_name [= view_option_value] [, ... ] )
ALTER VIEW [ IF EXISTS ] name RESET ( view_option_name [, ... ] )
```

## Description
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`ALTER VIEW` changes various auxiliary properties of a view. (If you want to modify the view's defining query, use `CREATE OR REPLACE VIEW`.) You must own the view to use `ALTER VIEW`. To change a view's schema, you must also have `CREATE` privilege on the new schema. To alter the owner, you must be able to `SET ROLE` to the new owning role, and that role must have `CREATE` privilege on the view's schema.

## Parameters
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**`name`**  
The name (optionally schema-qualified) of an existing view. 

**`column_name`**  
Name of an existing column, or new name for an existing column.

**`IF EXISTS`**  
Don't throw an error if the view doesn't exist. A notice is issued in this case.

**`SET/DROP DEFAULT`**  
These forms set or remove the default value for a column. The default value for a view column is substituted into any `INSERT` or `UPDATE` command where the target is the view.

**`new_owner`**  
The user name of the new owner of the view.

**`new_name`**  
The new name for the view.

**`new_schema`**  
The new schema for the view.

**`SET ( view_option_name [= view_option_value] [, ... ] )`**  
Sets a view option. The following are supported options:  
+ `check_option (enum)` - Changes the check option of the view. The value must be `local` or `cascaded`.
+ `security_barrier (boolean)` - Changes the security-barrier property of the view.
+ `security_invoker (boolean)` - Changes the security-invoker property of the view.

**`RESET ( view_option_name [, ... ] )`**  
Resets a view option to its default value.

## Examples
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Renaming the view `foo` to `bar`:

```
ALTER VIEW foo RENAME TO bar;
```

Attaching a default column value to an updatable view:

```
CREATE TABLE base_table (id int, ts timestamptz);
CREATE VIEW a_view AS SELECT * FROM base_table;
ALTER VIEW a_view ALTER COLUMN ts SET DEFAULT now();
INSERT INTO base_table(id) VALUES(1);  -- ts will receive a NULL
INSERT INTO a_view(id) VALUES(2);  -- ts will receive the current time
```

## Compatibility
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`ALTER VIEW` is a PostgreSQL extension of the SQL standard that Aurora DSQL supports.