VIEWS SQL

---VIEWS--

---Database objects which are used to represent an SQL Query that can be used to fetch data from a single or multiple tables.

----Views are also known as virtual tables and always depend upon the base tables for their working.


---Views are used for 2 reasons.

---1)Simplify the querying process. Views represent the SQL Query and we don't have to write the query again and again.views do not have space allocated to them.


--2)Views also implement data security.

--example:-There may be a table with no select permissions on any of the columns.But a View can be created to allow the user to view selective data from a particular set of columns.

----Types of Views--

---1)Simple Views.
---2)Partitioned Views.
---3)Indexed Views.

--select * from salesdetails

create view vw as select * from salesdetails where sno=100

select * from vw
select * from salesdetails
insert vw values(656,800,'ffg')

alter view vw as select * from salesdetails where sno=100 with

check option

sp_helptext vw


drop view vw

---Partition Views

--They can be created on tables from same server or different server .

create  view vws as
select sno,salary from salesdetails

union all

select * from salesunion

select * from vws

--Read only views
--We can only view the data.Insert,delete,update  cannot be executed on these views.

--examples:-

--Aggregate function queries, distinct operator , union.

create view vwd as select count(*) as "count" from salesdetails

select * from vwd
--Error

insert vwd values(67)
delete from vwd where count=6


create  view vwf as select distinct(salary) from salesdetails

delete from vwf

sp_helptext vwf