Structured Query Language (SQL) DB Chapter 3 J.G. Zheng June 27th 2005

Overview SQL Language (SQL 92) Create Table Select All examples can be used with the “AmazonBook” database This database can be downloaded from the “Course Material” section in WebCT

Introduction/Review What is SQL Some facts about SQL Review: Database and DBMS (chapter 1) SQL is a standard language accepted by relational DBMS to perform database operations Some facts about SQL SQL 92 is the most commonly supported version English-like (not programming) Case insensitive Venders have different implementations

Concepts Review Relational model concepts review Relation : Table Row : Record Column : Field (Attribute)

Create Table Statement CREATE TABLE TableName ( Column 1 Definition, Column 2 Definition, …, PRIMARY KEY (Column, [Column]) )

Column Definition Column Definition Format Example ColumnName DataType BookTitle Text(200) NumberofPages Integer ListPrice Currency

Common Data Types Numeric Character/String Date INTEGER, SMALLINT DECIMAL(i,j), NUMBER(i,j) Character/String CHAR(n), VARCHAR(n) Date DATE, DATETIME See textbook page 42-43 for data types implemented in Access

Create Table Example CREATE TABLE Books ( Title VARCHAR(100), Publisher VARCHAR(50), ISBN CHAR(13), Price DECIMAL(6,2), Year INTEGER, PRIMARY KEY (ISBN) ) Exercise: understand the statement What is the name of this table? How many columns are there? Which one is the primary key? How many characters are allowed for a book title? What is the maximum price that can be entered for any book?

SELECT Statement SELECT statement retrieves data from database (query) The result is usually another table We will learn Selection and projection Sorting Calculation Demo all examples in Access

SELECT Statement Syntax SELECT Column(s) or other expressions FROM Table(s) [WHERE …] [ORDER BY ColumnName] The order of the keyword is important

Simple SELECT Statement Syntax SELECT * (or a list of columns) FROM TableName Wild card: * Example SELECT * FROM Books SELECT BookTitle, ListPrice FROM Books

Use WHERE Clause Use WHERE clause to specify selection criteria Example SELECT * FROM Books WHERE ListPrice = 29.99 SELECT BookTitle, ListPrice FROM Books WHERE ListPrice < 20 Comparison Operators “=“, “>”, “<“, “>=“, “<=“, “<>”

More Comparison Operators IN (value list) SELECT * FROM Books WHERE ListPrice IN (19.99, 29.99, 39.99) BETWEEN min AND max WHERE ListPrice BETWEEN 9.99 AND 19.99

String Pattern Match Fuzzy query using LIKE Example _ (underscore): single character wildcard ? in Access % (percentage): multiple character wildcard * in Access Example SELECT * FROM Books WHERE BookTitle LIKE '*information systems*'

Compound Conditions Use logical operators to connect multiple conditions AND: an intersection of the data sets OR: a union of the data sets Examples SELECT * FROM Books WHERE ListPrice <= 19.99 AND ListPrice >= 9.99 WHERE PubDate=#10/1/2003# OR PubDate=#10/1/2004# SELECT * from Books WHERE Publisher = 'Que' AND Binding = 'Paperback'

Sorting Syntax Examples ORDER BY Column(s) [ASC/DESC] SELECT * FROM Books ORDER BY PubDate ORDER BY Publisher DESC, PubDate

Calculation Calculating columns Example Calculated columns are not designed directly into the table Using +, -, *, / with columns and numbers Example SELECT BookTitle, ListPrice, ListPrice * 0.15 AS Discount FROM Books WHERE ListPrice * 0.15 > 20 Usage example: Order: unitprice*quantity

Built-in Functions Using these functions to do statistics Example MIN MAX COUNT AVG SUM Example SELECT COUNT(*) FROM Books SELECT AVG(ListPrice) FROM Books WHERE Publisher = 'Prentice Hall'

[Grouping] GROUP BY: doing math with groups SELECT COUNT(*) FROM Books WHERE Publisher = 'Prentice Hall'; SELECT COUNT(*) FROM Books WHERE Publisher = 'The MIT Press'; … Or: SELECT Publisher, COUNT(*) FROM Books GROUP BY Publisher

A Complete Query SELECT ISBN, BookTitle, ListPrice, Publisher FROM Books WHERE BookTitle like '*Information Systems*' AND PubDate > #1/1/2002# AND ListPrice < 100 ORDER BY ListPrice

Exercise Using the “AmazonBook” database, use SQL or QBE to answer the following questions. Which book is the most expensive? How many books are under $100 of list price? I am looking for a “database” book, no more than 50 dollars, and published after 1/1/2003; do you have any recommendations? I need the book title and its price. What is the price per page for the books published by Que? List the book title, price, number of pages and price for page, and sort by the price per page, descending Write out the potential results of these SQL statements

Updating Tables INSERT INTO UPDATE DELETE FROM Read this part yourself To add a new record UPDATE To change data DELETE FROM To delete records Read this part yourself

Summary SQL is a standard Relational DBMS language SQL statements CREATE TABLE SELECT WHERE clause DELETE FROM INSERT INTO UPDATE

Good Resources SQL Online Tutorial http://sqlcourse.com/ http://sqlcourse2.com/