norcom dating - Oracle updating through view
If you had defined a DEFAULT value of 10 on the DEPTNO field, then you could perform inserts. Loc FROM Emp e, Dept d /* JOIN operation */ WHERE e. A modifiable join view is a view that contains more than one table in the top-level FROM clause of the SELECT statement, and that does not contain any of the following: Any UPDATE, INSERT, or DELETE statement on a join view can modify only one underlying base table.
If you don’t want any DML operations to be performed on views, create them WITH READ ONLY option. When a user attempts to reference an invalid view, Oracle returns an error message to the user: ORA-04063: view 'view_name' has errors This error message is returned when a view exists but is unusable due to errors in its query (whether it had errors when originally created or it was created successfully but became unusable later because underlying objects were altered or dropped). For example: DROP VIEW Accounts_staff; Oracle allows you, with some restrictions, to modify views that involve joins. The following example shows an UPDATE statement that successfully modifies the EMP_DEPT_VIEW view: UPDATE Emp_dept_view SET Sal = Sal * 1.10 WHERE Deptno = 10; The following UPDATE statement would be disallowed on the EMP_DEPT_VIEW view: UPDATE Emp_dept_view SET Loc = 'BOM' WHERE Ename = 'SAMI'; This statement fails with an ORA-01779 error ("cannot modify a column which maps to a non key-preserved table"), because it attempts to modify the underlying DEPT table, and the DEPT table is not key preserved in the EMP_DEPT view.
If conditions later change so that the query of an invalid view can be executed, then the view can be recompiled and become valid.
However, now you realize that you must redefine the ACCOUNTS_STAFF view to correct the department number specified in the WHERE clause of the defining query, because it should have been 30.
To preserve the grants of object privileges that you have made, you can replace the current version of the ACCOUNTS_STAFF view with the following statement: CREATE OR REPLACE VIEW Accounts_staff AS SELECT Empno, Ename, Deptno FROM Emp WHERE Deptno = 30 WITH CHECK OPTION CONSTRAINT ica_Accounts_cnst; Replacing a view has the following effects: With some restrictions, rows can be inserted into, updated in, or deleted from a base table using a view.
Using an Access project or an Access database with a form bound to a view that contains statement attempting to modify columns in both the Products and Categories tables won't work (you'll get the error "View or function 'vw Categories Products' is not updateable because the In general, you'll want to make views that use joins read-only.
Allowing updates in views with joins is likely to confuse users because it's not intuitive that they can't update different columns on the same row. If you want users to be able to use views to update data, base the view on a single table, or use a stored procedure to perform the update.
select e.empno,e.ename,e.sal,e.deptno,d.dname,From emp e, dept d where e.deptno=d.deptno; So everytime we want to see emp details and department names where they are working we have to give a long join query.
Instead of giving this join query again and again, we can create a view on these table by using a CREATE VIEW command given below create view emp_det as select e.empno, e.ename,e.sal,e.deptno,d.dname,from emp e, dept d where e.deptno=d.deptno; Now to see the employee details and department names we don’t have to give a join query, we can just type the following simple query.The SQL UPDATE VIEW command can be used to modify the data of a view. An updatable view is one which allows performing a UPDATE command on itself without affecting any other table. The view is defined based on one and only one table. The view must include the PRIMARY KEY of the table based upon which the view has been created. The view should not have any field made out of aggregate functions. The view must not have any DISTINCT clause in its definition. The view must not have any GROUP BY or HAVING clause in its definition. The view must not have any SUBQUERIES in its definitions. If the view you want to update is based upon another view, the later should be updatable. Any of the selected output fields (of the view) must not use constants, strings or value expressions.Type FROM inserted) Is Null RETURN SELECT @Del Name = deleted. Type FROM inserted) = ' Company' UPDATE Customers SET Company Name = (SELECT Company Name FROM inserted) WHERE Customers.Company Name = @Del Name ELSE UPDATE Suppliers SET Company Name = (SELECT Company Name FROM inserted) WHERE Suppliers.Views are very powerful and handy since they can be treated just like any other table but do not occupy the space of a table.