What is a View? 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
SQL – Relations, Tables & Views 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
SQL – Create View 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’;
SQL – Querying View 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
SQL - Querying View con’t Query involving both view and table SELECT DISTINCT starName FROM ParamountMovie, StarsIn WHERE title = movieTitle AND year = movieYear; Table View
SQL - Querying View example Movie (title, year, length, inColor, studioName, producerC#) MovieExec (name, address, cert#, netWorth) CREATE VIEW MovieProd AS SELECT title, name FROM Movie, MovieExec WHERE producerC# = cert#; SELECT name FROM MovieProd WHERE title = ‘Gone With the Wind’; Same result as query from tables SELECT name FROM Movie, MovieExec WHERE producerC# = cert# AND title = ‘The War Of the World’;
SQL - Renaming Attributes in 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#;
SQL - Modifying View 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.
SQL – Modifying View (INSERT) 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’ NULL ‘Paramount’ NULL
SQL - Modifying View (DELETE) 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’;
SQL - Modifying View (UPDATE) 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’;
SQL – View (DROP) 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
SQL - D ownload MySQL Go to and download:http://dev.mysql.com/downloads/ MySQL (Windows User / version a, alpha has bug that keep shutting down the service) MySQL Administrator MySQL Query Browser
SQL – Install MySQL During the installation – – you can to fast installation – Will run Configuration Wizard right after installation automatically – If the service won’t start, press, then run Configuration Wizard manually again Run MySQL Server Instance Config Wizard from windows menu – – use default setting unless you know what you are doing – Modify Security Setting (option: you can start service without doing this) – Execute If there is an error, try press to go back, then press to again – TCP / IP Networking – Try different port number if you are using networking.
SQL - MySQL Administrator MySQL Administrator come with MySQL System Tray Monitor allow you to configure your server Run MySQL Administrator – – For the first time, you may not have “Stored connection,” you can and give the Connection name. – Server Host: type “localhost” If you don’t use networking
SQL - MySQL Query Browser Run MySQL Query Browser – Give a name for the Default Schema Schema means Database instance – You can type command line into the top box or right Click on schemata to create new table
SQL - Bibliography First Course In Database Systems, Jeffery D. Ullman and Jennifer Widom,1997 Prentice Hall, Inc.
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