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SQL Anywhere 10.0.1 » SQL Anywhere Server - SQL Reference » SQL Statements

CREATE VARIABLE statement Next Page

CREATE VIEW statement


Use this statement to create a view on the database. Views are used to give a different perspective on the data, even though it is not stored that way.

Syntax

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

Parameters

view-name    The view-name is an identifier. The default owner is the current user ID.

column-name    The columns in the view are given the names specified in the column-name list. If the column name list is not specified, the view columns are given names from the select list items. To use the names from the select list items, each item must be a simple column name or have an alias-name specified (see SELECT statement). All items in the select list must have unique names.

AS clause    The SELECT statement on which the view is based. The SELECT statement must not refer to local temporary tables. Also, the SELECT statement can have an ORDER BY or GROUP BY clause, and can be a UNION. However, note that in some cases, particularly when combined with the FIRST or TOP clause, using a SELECT with an ORDER BY clause does affect the results of a view definition.

WITH CHECK OPTION clause    The WITH CHECK OPTION clause rejects any updates and inserts to the view that do not meet the criteria of the views as defined by its SELECT statement.

Remarks

The CREATE VIEW statement creates a view with the given name. You can create a view owned by another user by specifying the owner. You must have DBA authority to create a view for another user.

A view name can be used in place of a table name in SELECT, DELETE, UPDATE, and INSERT statements. Views, however, do not physically exist in the database as tables. They are derived each time they are used. The view is derived as the result of the SELECT statement specified in the CREATE VIEW statement. Table names used in a view should be qualified by the user ID of the table owner. Otherwise, a different user ID might not be able to find the table or might get the wrong table.

Views can be updated unless the SELECT statement defining the view contains a GROUP BY clause, an aggregate function, or involves a UNION statement. An update to the view causes the underlying table(s) to be updated.

Typically, a view references tables and views (and their respective attributes) that are defined in the catalog. However, a view can also reference SQL variables. In this case, when a query that references the view is executed, the value of the SQL variable is used. Views that reference SQL variables are called parameterized views since the variables act as parameters to the execution of the view.

Parameterized views offer an alternative to embedding the body of an equivalent SELECT block in a query as a derived table in the query's FROM clause. Parameterized views can be especially useful for queries embedded in stored procedures where the SQL variables referenced in the view are input parameters to the procedure.

It is not necessary for the SQL variable to exist when the CREATE VIEW statement is executed. However, if the SQL variable is not defined when a query that refers to the view is executed, a Column Not Found error is returned.

Permissions

Must have RESOURCE authority and SELECT permission on the tables in the view definition.

Side effects

Automatic commit.

See also
Standards and compatibility
Example

The following example creates a view showing information for male employees only. This view has the same column names as the base table.

CREATE VIEW MaleEmployees
AS SELECT *
FROM Employees
WHERE Sex = 'M';

The following example creates a view showing employees and the departments they belong to.

CREATE VIEW EmployeesAndDepartments
  AS SELECT Surname, GivenName, DepartmentName
  FROM Employees JOIN Departments
  ON Employees.DepartmentID = Departments.DepartmentID;

The following example creates a parameterized view based on the variables var1 and var2, which are neither attributes of the Employees nor Departments tables:

CREATE VIEW EmployeesByState
  AS SELECT Surname, GivenName, DepartmentName
  FROM Employees JOIN Departments
  ON Employees.DepartmentID = Departments.DepartmentID
  WHERE Employees.State = var1 and Employees.Status = var2;

Variables can appear in the view's SELECT statement in any context where a variable is a permitted expression. For example, the following parameterized view utilizes the parameter var1 as the pattern for a LIKE predicate:

CREATE VIEW ProductsByDescription
  AS SELECT *
  FROM Products
  WHERE Products.Description LIKE var1;

To use this view, the variable var1 must be defined before the query referencing the view is executed. For example, the following could be placed in a procedure, function, or a batch statement:

BEGIN
DECLARE var1 CHAR(20);
SET var1 = '%cap%';
SELECT * FROM ProductsByDescription
END