SQL

Originally developed by IBM Standardized in 80’s by ANSI and ISO Language to access relational database and English-like non-procedural Predominant language for database access Implemented on Oracle, Sybase, Informix,DB/2, SQL Server

Uses of SQL Code As data definition language (DDL) –Create table, drop table, create index, create constraints, insert record As data manipulation language (DML) –Update table, insert record, delete record As data query language –Select, create view As database management language (Data control language) –Create user, grant privileges, revoke privileges

SELECT command For retrieving records from one or more tables Minimal Syntax (to retrieve one field from one table) SELECT FROM

SELECT SELECT [as var1] FROM WHERE GROUP BY ORDER By Expression can be a field name, or constant or system variable or string or arithmetic or logical expressions that use expressions

Boolean conditions Used to filter records for output Evaluates to be True or False Applied to each record in the table Only those that evaluates True are output Examples CatID = ‘3’ Videos.Year = 1994 and Rating >3 Rating<3 or Stars <= 2

SELECT Example Find videos with rating of 4 or more SELECT videos.title, rating FROM Videos WHERE videos.rating >= 4

SELECT Example using Alias Alias is an alternative column or table name SELECT Videos.Title AS MustSeeVideos, videos.Stars FROM Videos WHERE videos.star = 5;

SELECT Example Using a Function Using the COUNT aggregate function to find totals SELECT COUNT(VideoID) FROM Videos WHERE CatID = ‘2’;

SELECT Example – Boolean Operators AND, OR, and NOT Operators for customizing conditions in WHERE clause SELECT Videos.Title, videos.Cast FROM Videos WHERE Videos.cast LIKE ‘*Gibson*’ OR Videos.cast like ‘*Williams’

Sorting Results with the ORDER BY Clause Sort the results first by STATE, and within a state by CUSTOMER_NAME SELECT Videos.Title, Videos.Director From Videos ORDER BY Director, CUSTOMER_NAME;

Comparing with multiple values SELECT Videos.Title, Videos.Director, CatID From Videos where catID in ('2', '3', '5') ORDER BY Director;

Comparing with multiple values SELECT Videos.Title, Videos.Director, Year From Videos where year between 1980 and 1990 ORDER BY Director;

Categorizing Results Using the GROUP BY Clause For use with aggregate functions SELECT CatID, COUNT(VideoID) FROM Videos GROUP BY CatID;

Qualifying Results by Categories Using the HAVING Clause For use with GROUP BY SELECT CatID, COUNT(VideoID) FROM Videos GROUP BY CatID HAVING COUNT(VideoID) > 1; Like a WHERE clause, but it operates on groups (categories), not on individual rows. Here, only those groups with total numbers greater than 1 will be included in final result