Oracle9i SQL Reference
Release 1 (9.0.1)

Part Number A90125-01
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SQL Statements:



Use the CREATE VIEW statement to define a view, which is a logical table based on one or more tables or views. A view contains no data itself. The tables upon which a view is based are called base tables.

You can also create an object view or a relational view that supports LOB and object datatypes (object types, REFs, nested table, or varray types) on top of the existing view mechanism. An object view is a view of a user-defined type, where each row contains objects, each object with a unique object identifier.

See Also:



To create a view in your own schema, you must have CREATE VIEW system privilege. To create a view in another user's schema, you must have CREATE ANY VIEW system privilege.

To create a subview, you must have UNDER ANY VIEW system privilege or the UNDER object privilege on the superview.

The owner of the schema containing the view must have the privileges necessary to either select, insert, update, or delete rows from all the tables or views on which the view is based. The owner must be granted these privileges directly, rather than through a role.

To use the basic constructor method of an object type when creating an object view, one of the following must be true:

Partition Views

Partition views were introduced in Oracle Release 7.3 to provide partitioning capabilities for applications requiring them. Partition views are supported in Oracle9i so that you can upgrade applications from Release 7.3 without any modification. In most cases, subsequent to migration to Oracle9i you will want to migrate partition views into partitions.

In Oracle9i, you can use the CREATE TABLE statement to create partitioned tables easily. Partitioned tables offer the same advantages as partition views, while also addressing their shortcomings. Oracle recommends that you use partitioned tables rather than partition views in most operational environments.

See Also:




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Text description of create_view

table_or_view_constraint and column_constraint: See constraint_clause.


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Text description of object_view_clause

subquery: See SELECT.


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Text description of subquery_restriction_clause

Keywords and Parameters


Specify OR REPLACE to re-create the view if it already exists. You can use this clause to change the definition of an existing view without dropping, re-creating, and regranting object privileges previously granted on it.

INSTEAD OF triggers defined in the view are dropped when a view is re-created.

If any materialized views are dependent on view, those materialized views will be marked UNUSABLE and will require a full refresh to restore them to a usable state. Invalid materialized views cannot be used by query rewrite and cannot be refreshed until they are recompiled.

See Also:



Specify FORCE if you want to create the view regardless of whether the view's base tables or the referenced object types exist or the owner of the schema containing the view has privileges on them. These conditions must be true before any SELECT, INSERT, UPDATE, or DELETE statements can be issued against the view.

If the view definition contains any constraints, CREATE VIEW ... FORCE will fail if the base table does not exist or the referenced object type does not exist. CREATE VIEW ... FORCE will also fail if the view definition references a constraint that does not exist.


Specify NOFORCE if you want to create the view only if the base tables exist and the owner of the schema containing the view has privileges on them. This is the default.


Specify the schema to contain the view. If you omit schema, Oracle creates the view in your own schema.


Specify the name of the view or the object view.

Restriction: If a view has INSTEAD OF triggers, any views created on it must have INSTEAD OF triggers, even if the views are inherently updatable.


Specify names for the expressions selected by the view's query. The number of aliases must match the number of expressions selected by the view. Aliases must follow the rules for naming Oracle schema objects. Aliases must be unique within the view.

If you omit the aliases, Oracle derives them from the columns or column aliases in the view's query. For this reason, you must use aliases if the view's query contains expressions rather than only column names. Also, you must specify aliases if the view definition includes constraints.

Restriction: You cannot specify an alias when creating an object view.

See Also:

"Syntax for Schema Objects and Parts in SQL Statements" 

table_or_view_constraint and column_constraint

You can specify constraints on views and object views. You define the constraint at the view level using the table_or_view_constraint clause. You define the constraint at the column or attribute level using the column_constraint clause after the appropriate alias.

View constraints (at the view and at the column or attribute level) are declarative only. That is, Oracle does not enforce them. However, operations on views are subject to the integrity constraints defined on the underlying base tables, so you can enforce constraints on views through constraints on base tables.

View constraints are a subset of table constraints and are subject to a number of restrictions.

See Also:

constraint_clause for more information on constraints in general and on restrictions on view constraints 


The object_view_clause lets you define a view on an object type.

OF type_name Clause

Use this clause to explicitly create an object view of type type_name. The columns of an object view correspond to the top-level attributes of type type_name. Each row will contain an object instance and each instance will be associated with an object identifier (OID) as specified in the WITH OBJECT IDENTIFIER clause. If you omit schema, Oracle creates the object view in your own schema.


Use the WITH OBJECT IDENTIFIER clause to specify a top-level (root) object view. This clause lets you specify the attributes of the object type that will be used as a key to identify each row in the object view. In most cases these attributes correspond to the primary key columns of the base table. You must ensure that the attribute list is unique and identifies exactly one row in the view.


If the object view is defined on an object table or an object view, you can omit this clause or specify DEFAULT.


Specify DEFAULT if you want Oracle to use the intrinsic object identifier of the underlying object table or object view to uniquely identify each row.


For attribute, specify an attribute of the object type from which Oracle should create the object identifier for the object view.

UNDER Clause

Use the UNDER clause to specify a subview based on an object superview.

To learn whether a view is a superview or a subview, query the SUPERVIEW_NAME column of the USER_, ALL_, or DBA_VIEWS data dictionary views.


AS subquery

Specify a subquery that identifies columns and rows of the table(s) that the view is based on. The select list of the subquery can contain up to 1000 expressions.

If you create views that refer to remote tables and views, the database links you specify must have been created using the CONNECT TO clause of the CREATE DATABASE LINK statement, and you must qualify them with schema name in the view subquery.

Restrictions on the view subquery:

The preceding restrictions apply to materialized views as well.

Notes on Creating Updatable Views:

An updatable view is one you can use to insert, update, or delete base table rows. You can create a view to be inherently updatable, or you can create an INSTEAD OF trigger on any view to make it updatable.

To learn whether and in what ways the columns of an inherently updatable view can be modified, query the USER_UPDATABLE_COLUMNS data dictionary view. (The information displayed by this view is meaningful only for inherently updatable views.)


Use the subquery_restriction_clause to restrict the subquery in one of the following ways:


Specify WITH READ ONLY if you want no deletes, inserts, or updates to be performed through the view.


Specify WITH CHECK OPTION to guarantee that inserts and updates performed through the view will result in rows that the view subquery can select. The CHECK OPTION cannot make this guarantee if:

CONSTRAINT constraint

Specify the name of the CHECK OPTION constraint. If you omit this identifier, Oracle automatically assigns the constraint a name of the form SYS_Cn, where n is an integer that makes the constraint name unique within the database.


Basic View Example

The following statement creates a view of the sample table employees named emp_view. The view shows the employees in department 20 and their annual salary:

CREATE VIEW emp_view AS 
   SELECT last_name, salary*12 annual_salary
   FROM employees 
   WHERE department_id = 20;

The view declaration need not define a name for the column based on the expression sal*12, because the subquery uses a column alias (annual_salary) for this expression.

View with Constraints Example

The following statement creates a restricted view of the sample table hr.employees and defines a unique constraint on the email view column and a primary key constraint for the view on the emp_id view column:

CREATE VIEW emp_sal (emp_id, last_name, 
   AS SELECT employee_id, last_name, email FROM employees;
Updatable View Example

The following statement creates an updatable view named clerk of all sales and purchasing clerks in the employees table. Only the employees' IDs, last names, department numbers, and jobs are visible in this view, and these columns can be updated only in rows where the employee is a king of clerk:

   SELECT employee_id, last_name, department_id, job_id 
   FROM employees
   WHERE job_id = 'PU_CLERK' 
      or job_id = 'SH_CLERK' 
      or job_id = 'ST_CLERK';

This view lets you change the job_id of a purchasing clerk to purchasing manager (PU_MAN):

UPDATE clerk SET job_id = 'PU_MAN' WHERE employee_id = 118;

The next example creates the same view WITH CHECK OPTION. You cannot subsequently insert a new row into clerk if the new employee is not a clerk. You can update an employee's job_id from one type of clerk to another type of clerk, but the update above would fail, because the view cannot access employees with non-clerk job_id.

   SELECT employee_id, last_name, department_id, job_id 
   FROM employees
   WHERE job_id = 'PU_CLERK' 
      or job_id = 'SH_CLERK' 
      or job_id = 'ST_CLERK'
Join View Example

A join view is one whose view subquery contains a join. If at least one column in the join has a unique index, then it may be possible to modify one base table in a join view. You can query USER_UPDATABLE_COLUMNS to see whether the columns in a join view are updatable. For example:

CREATE VIEW locations_view AS
   SELECT d.department_id, d.department_name, l.location_id,
   FROM departments d, locations l
   WHERE d.location_id = l.location_id;

SELECT column_name, updatable 
  FROM user_updatable_columns
  WHERE table_name = 'LOCATIONS_VIEW';

COLUMN_NAME                    UPD
------------------------------ ---
DEPARTMENT_ID                  YES
DEPARTMENT_NAME                YES
LOCATION_ID                    NO
CITY                           NO

In the above example, the primary key index on the location_id column of the locations table is not unique in the locations_view view. Therefore, locations is not a key-preserved table and columns from that base table are not updatable.

INSERT INTO locations_view VALUES
   (999, 'Entertainment', 87, 'Roma');
INSERT INTO locations_view VALUES
ERROR at line 1:
ORA-01776: cannot modify more than one base table through a join 

You can insert, update, or delete a row from the departments base table, because all the columns in the view mapping to the departments table are marked as updatable and because the primary key of departments is retained in the view.

INSERT INTO locations_view (department_id, department_name)
   VALUES (999, 'Entertainment');

1 row created.


You cannot insert into the table using the view unless the view contains all NOT NULL columns of all tables in the join, unless you have specified DEFAULT values for the NOT NULL columns. 

See Also:

Oracle9i Application Developer's Guide - Fundamentals for more information on updating join views 

Read-Only View Example

The following statement creates a read-only view named customer of the oe.customers table. Only the customers' last names, language, and credit limit are visible in this view:

CREATE VIEW customer (name, language, credit)
      AS SELECT cust_last_name, nls_language, credit_limit
      FROM customers
Object View Example

The following example shows the creation of the type inventory_typ in the oc schema, and the oc_inventories view that is based on that type:

    ( product_id          number(6) 
    , warehouse           warehouse_typ
    , quantity_on_hand    number(8)
    ) ;

CREATE OR REPLACE VIEW oc_inventories OF inventory_typ 
   AS SELECT i.product_id, 
     warehouse_typ(w.warehouse_id, w.warehouse_name, w.location_id),
   FROM inventories i, warehouses w
   WHERE i.warehouse_id=w.warehouse_id;

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