SQL Training in Ambala ! Batra Computer Centre

Website: www.batracomputercentre.comPh. No.: 8222066670, 4000670
Email: info.jatinbatra@gmail.com

 The IBM’s System/R was not the first DBMS. The
first to market was Relational Software's product
named Oracle
 The second was Relational Technology's Ingres.
 IBM then released improved products in 1982
named SQL/DS and DB2. Oracle and DB2 in nth
generation forms while the Ingres technology was
bought by Computer Associates

 SQL is a open language without corporate ownership.
 The ANSI-SQL (American National Standards Institute)
group has published three standards over the years:
SQL89 (SQL1)
SQL92 (SQL2)
SQL99 (SQL3)
 The majority of the language has not changed
through these updates.
 The SQL standard from ANSI is considered the "pure"
SQL and called ANSI-SQL.

 Every DBMS vendor wants their products to be different. So most
products offers extra features, these additions are generally not
compatible with competitor's SQL products.
 It is always safest to stick with pure SQL
 The enhancements are not all bad because these extensions are
very useful.
 For example, most DBMS sold today have an automatic way to
assign a serial number feature since serial numbering is so
common. However, the method of implementation is not
uniform.

 In SQL, a VIEW is a virtual relation based on the result-set of a
SELECT statement.
 A view contains rows and columns, just like a real table. The fields
in a view are fields from one or more real tables in the database.
In some cases, we can modify a view and present the data as if
the data were coming from a single table.
 Syntax:
 CREATE VIEW view_name AS
 SELECT column_name(s)
 FROM table_name
 WHERE condition

When we say Relation, it could be a Table or a View. There are three
kind of relations:
1. Stored relations tables
We sometimes use the term “base relation” or “base table”
2. Virtual relations views
3. Temporary results

Example: Create a view with title and year and made by Paramount
studio.
Movie (title, year, length, inColor, studioName, producerC#)
CREATE VIEW ParamountMovie AS
SELECT title,year
FROM Movie
WHERE studioName = ‘Paramount’;

 A view could be used from inside a query, a stored procedure, or
from inside another view. By adding functions, joins, etc., to a view,
it allows us to present exactly the data we want to the user.
SELECT title
FROM ParamountMovie
WHERE year = ‘1979’;
 Have same result as
SELECT title
FROM Movie
WHERE studioName = ‘Paramount’ AND year = ‘1979’;
View
Table

 Query involving both view and table
SELECT DISTINCT starName
FROM ParamountMovie, StarsIn
WHERE title = movieTitle AND year = movieYear;
Table
View

Sometime, we might want to distinguish attributes by
giving the different name.
CREATE VIEW MovieProd (movieTitle, prodName) AS
SELECT title, name
FROM Movie, MovieExec
WHERE producerC# = cert#;

When we modify a view, we actually modify a table through a view.
Many views are not updateable. Here are rules have been
defined in SQL for updateable views:
 selecting (SELECT not SELECT DISTINCT) some attributes from
one relation R (which may itself be an updateable view)
 The WHERE clause must not involve R in a subquery.
 The list in the SELECT clause must include enough
attributes that will allow us to insert tuples into the view as
well as table. All other attributes will be filled out with
NULL or the proper default values.

INSERT INTO ParamountMovie
VALUES (‘Star Trek’, 1979);
To make the view ParamountMovie updateable, we need to add
attribute studioName to it’s SELECT clause because it makes more
sense if the studioName is Paramount instead of NULL.
CREATE VIEW ParamountMovie AS
SELECT studioName, title, year
FROM Movie
WHERE studioName = ‘Paramount’;
Then
INSERT INTO ParamountMovie
VALUES (‘Paramount’, ‘Star Trek’, 1979);
Title year length inColor studioName producerC#
‘Star Trek’ 1979 0 NULL ‘Paramount’ NULL

 Suppose we wish to delete all movies with “Trek” in
their title from the updateable view ParamountMovie.
DELETE FROM ParamountMovie
WHERE title LIKE ‘%Trek%’;
It is turned into the base table delete
DELETE FROM Movie
WHERE title LIKE ‘%Trek%’ AND studioName = ‘Paramount’;

 UPDATE from an updateable view
UPDATE ParamountMovie
SET year = 1979
WHERE title = ‘Star Trek the Movie’;
It is turned into the base table update
UPDATE Movie
SET year = 1979
WHERE title = ‘Star Trek the Movie’ AND studioName =
‘Paramount’;

 DROP view: All views can be dropped, whether or not the view
is updateable.
DROP VIEW ParamountMovie;
 DROP VIEW does not affect any tuples of the underlying
relation (table) Movie.
 However, DROP TABLE will delete the table and also make the
view ParamountMovie unusable.
DROP TABLE Movie

ADDRESS:
SCO -15, Dayal Bagh,
Near Hanuman Mandir
Ambala Cantt-133001
Haryana
Ph. No.: 9729666670, 8222066670 &0171-4000670
Email ID: info.jatinbatra@gmail.com
Website: www.batracomputercentre.com

SQL Training in Ambala ! Batra Computer Centre

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SQL Training in Ambala ! Batra Computer Centre