Concepts of Database Management Seventh Edition

Concepts of Database ManagementSeventh Edition Chapter 3 The Relational Model 2: SQL

Objectives • Introduce Structured Query Language (SQL) • Use simple and compound conditions in SQL • Use computed fields in SQL • Use built-in SQL functions • Use subqueries in SQL

Objectives (continued) • Group records in SQL • Join tables using SQL • Perform union operations in SQL • Use SQL to update database data • Use an SQL query to create a table in a database

Introduction • SQL (Structured Query Language) • Allows users to query a relational database • Must enter commands to obtain the desired results • Standard language for relational database manipulation

Getting Started with SQL • If you are completing the work in this chapter using Microsoft Office Access 2007, Microsoft Office Access 2010, or MySQL version 4.1 or higher, the following sections contain specific information about your DBMS

Getting Started with Microsoft Office Access 2007 and 2010 • If you are using the Access 2007 or 2010 version of the Premiere Products database provided with the Data Files for this text: • Tables in the database have already been created • You will not need to execute the CREATE TABLE commands to create the tables or the INSERT commands to add records to the tables

Getting Started with Microsoft Office Access 2007 and 2010 (continued) • To execute SQL commands shown in the figures in Access 2007 or Access 2010: • Open the Premiere Products database • Click the Create tab on the Ribbon • Click the Query Design button in the Other group • Click the Close button in the Show Table dialog box • Click the View button arrow in the Results group on the Query Design Tools tab, then click SQL View • The Query1 tab displays the query in SQL view, ready for you to type your SQL commands

Getting Started with MySQL • MySQL-Premiere script provided with the Data Files for this text will: • Activate the database • Create the tables • Insert the records • To run a script in MySQL: • Type the SOURCE command followed by the name of the file • Press the Enter key

Getting Started with MySQL (continued) • Before typing commands in MySQL, you must activate the database by typing the USE command followed by the name of the database • The most recent command entered in MySQL is stored in a special area of memory called the statement history

Table Creation • SQL CREATE TABLE command • Creates a table by describing its layout • Typical restrictions placed on table and column names by DBMS • Names cannot exceed 18 characters • Names must start with a letter • Names can contain only letters, numbers, and underscores (_) • Names cannot contain spaces

Table Creation (continued) • INTEGER • Number without a decimal point • SMALLINT • Uses less space than INTEGER • DECIMAL(p,q) • P number of digits; q number of decimal places • CHAR(n) • Character string n places long • DATE • Dates in DD-MON-YYYY or MM/DD/YYYY form

Simple Retrieval • SELECT-FROM-WHERE: SQL retrieval command • SELECT clause: lists fields to display • FROM clause: lists table or tables that contain data to display in query results • WHERE clause (optional): lists any conditions to be applied to the data to retrieve • Simple condition: field name, a comparison operator, and either another field name or a value

Simple Retrieval (continued) • Retrieving all fields and all records • Syntax: SELECT * FROM <table> • Example 1: SELECT * FROM Customer • Example 2: SELECT * FROM Rep • Retrieving specific field(s) • Syntax: SELECT <field1>, <field2>,..<fieldn> FROM <table> • Example 1: SELECT Customername, City, State FROM Customer • Example 2: SELECT Repnum, Lastname, Firstname, Commission, Rate FROM Rep

Non-Graded Exercise • Show all the fields and records from Rep table • Show all fields and records Part table • Show the Last name and First name of all Sales Rep from Rep table • Show the Part number, Description, On Hand Quantity and Price from Part table

Simple Retrieval – Filtering Records • Filtering records to retrieve using WHERE clause • Syntax: SELECT * FROM <table> • Example 1: (Filtering records with a Text/String field) SELECT * FROM Customer WHERE City=‘Grove’ • Example 2: (Filtering records with a Numeric field) SELECT * FROM Customer WHERE CreditLimit=7500 • Example 3: (Filtering records using specific fields) SELECT Customername, City WHERE City = ‘Grove’ • Example 4: (Filtering records using not equal) SELECT * FROM City WHERE City <> ‘Fillmore’ • Note : If it is a string or a text the value should have a quote like in ‘Grove’ but if it is numeric do not put a quote.

Simple Retrieval (continued) FIGURE 3-6: SQL query with WHERE condition

Simple Retrieval (continued) FIGURE 3-7: Query results

Relational Operators Date Comparisons

Non-Graded Exercise • Show all Customers that comes from the City of Altonville from Customer table • Show all products from Part table whose class is AP • Show all Customers whose Balance is greater than 7000 from Customer table • Show all Customers whose Credit Limit is above or equal to 7500 from Customer table • Show all Customers whose balance is less than 500 from Customer table • Show all orders from Orders table whose order is beyond 10/20/2013

Compound Conditions • Compound condition • Connecting two or more simple conditions using one or both of the following operators: AND and OR • Preceding a single condition with the NOT operator • Connecting simple conditions using AND operator • All of the simple conditions must be true for the compound condition to be true • Connecting simple conditions using OR operator • Any of the simple conditions must be true for the compound condition to be true

AND – Truth Table • In order for AND to be true all conditions/expressions should be true

AND – Truth Table (Example) • Example : Age>20 AND State=‘Pohnpei’

OR – Truth Table • In order for OR to be True at least one conditions/expressions should be true

OR – Truth Table (Example) • Example : Age>20 OR State=‘Pohnpei’

Compound Conditions (continued) FIGURE 3-15: Compound condition that uses the AND operator FIGURE 3-16: Query results

Compound Conditions (continued) FIGURE 3-17: Compound condition that uses the OR operator FIGURE 3-18: Query results

Non-Graded Exercise • Show all products from Part table whose class is AP and its price is above $400 • Show all Customers that comes from either the City of Fillmore or Grove from Customer table • Show all Customers whose Credit Limit is $7,500 but its Balance is above $5,000 from Customer table • Show all products whose warehouse is from either 1 or 2 • Show all products whose On hand quantity is above 20 and coming from Warehouse no. 3

Compound Conditions (continued) • Preceding a condition by NOT operator • Reverses the truth or falsity of the original condition • BETWEEN operator • Value must be between the listed numbers

Compound Conditions (continued) • Using NOT operator • Example 1: SELECT * FROM Customer WHERE NOT City=‘Grove’ • Example 2: SELECT * FROM Customer WHERE NOT CreditLimit=10000 • Using BETWEEN operator • Example 1: SELECT * FROM Customer WHERE Balance BETWEEN 5000 AND 10000 • Example 2: SELECT * FROM Orders WHERE Orderdate BETWEEN #10/20/2013# AND #10/21/2013

Non-Graded Exercise • Show all products from Part whose Class is not from AP • Show all products from Part whose Warehouse is not from Warehouse number 3 • Show all customers from Customer whose sales representative is not Repnum no. 65 • Show all products from Part whose Price is from $300 to $600. • Show all products from Part whose On hand quantity is from 20 to 50

Computed Fields • Computed field or calculated field • Field whose values you derive from existing fields • Can involve: • Addition (+) • Subtraction (-) • Multiplication (*) • Division (/)

Computed Fields (continued) • Numeric Computed Fields • Example 1: Computing the Net by deducting Credit Limit from Balance SELECT Customername, (Balance-CreditLimit) as Net FROM Customer • Example 2: Computing the Running Total by Multiplying On hand quantity with Price SELECT Partnum, Description, OnHand * Price as RunningTotal FROM Part • Non-numeric Computed Field • Example 1: Concatenating or Joining Last name and First name of the Sales as Full Name SELECT Repnum, Lastname + “, “ + Firstname as Fullname FROM Rep

Computed Fields (continued) FIGURE 3-25: SQL query with a computed field and condition FIGURE 3-26: Query results

Non-Graded Exercise • Show customer name and a computed field name Net using the formula CreditLimit – Balance from Customer table. • Get the Running Total from each order by multiplying Number Ordered and Quoted Price of the Orderline table. Aside from the Running Total show also the Order Number. • Get the Running Total per product from Part table by multiplying Quantity on Hand by price. Show also the Description of the product. • Make a concatenated field for Street, City, State and Zip fields and named it Address, from Customer table. Show also the Customer name before the address.

Using Special Operators (LIKE and IN) • Wildcards in Access SQL • Asterisk (*): collection of characters • Question mark (?): any individual character • Wildcards in MySQL • Percent sign (%): any collection of characters • Underscore (_): any individual character • To use a wildcard, include the LIKE operator in the WHERE clause • IN operator provides a concise way of phrasing certain conditions

Using LIKE operator and wildcards • Using asterisk for collection of characters pattern • Example 1: Displays customer whose name starts with letter B SELECT * FROM Customer WHERE customername LIKE ‘B*’ • Example 2: Displays customer whose name starts with the word Brook SELECT * FROM Customer WHERE customername LIKE ‘Brook*’ • Using question mark for individual/single character • Example 1: Display orders whose partnum starts with letter K followed by any 3 characters. SELECT * FROM Orderline WHERE partnum LIKE ‘K???’ • Example 2: Display product whose class startswith letter A followed by one character. SELECT * FROM Part WHERE class LIKE ‘A?’

Using the IN operator • Example 1: Displays customer whose credit limit is either $5,000 or $10,000 or $15,000 SELECT * FROM Customer WHERE creditlimit IN(5000,10000,15000) • Example 2: Displays customer who comes from the City of Grove, Crystal, Fillmore or Northfield SELECT * FROM Customer WHERE city IN(‘Grove’,’Crystal’,’Fillmore’,’Northfield’)

Non-Graded Exercise • Show all products from Part table that starts with letter ‘D’ • Show all customers from Customer table whose Street starts with 28 • Using IN show products whose class is AP or SG from Part table • Using IN show customers whose Credit Limit is either 5000, 10000 or 15000.

Sorting • Sort data using the ORDER BY clause • Sort key: field on which to sort data • When sorting data on two fields: • Major sort key (or primary sort key): more important sort key • Minor sort key (or secondary sort key): less important sort key

Using the ORDER BY statement • Example 1: Displays customer sorted by customer name SELECT * FROM Customer ORDER BY customername • Example 2: Displays sales rep sorted by Lastname then Firstname SELECT * FROM Rep ORDER BY Lastname, Firstname • Example 3: Displays sales rep sorted by Lastname in descending order SELECT * FROM Rep ORDER BY Lastname DESC • Example 4: Displays customer sorted by City whose Credit Limit is $10,000 SELECT * FROM Customer WHERE CreditLimit = 10000 ORDER BY city

Non-Graded Exercise • Show all products from Part table and sort it according to Product name • Show all products from Part table and sort it according to Warehouse and then product name • Show all products ordered from Orderline table and sort it according to Number of product ordered and in Descending order

Built-in Functions • Built-in functions (aggregate functions) in SQL • COUNT: calculates number of entries • SUM or AVG: calculates sum or average of all entries in a given column • MAX or MIN: calculates largest or smallest values respectively

Using Aggregate Functions (COUNT, SUM, AVG, MAX, MIN) • Example 1: Count all how many customers in Customer table SELECT COUNT(*) as CustomerCount FROM Customer • Example 2: Count how many customers from the City of Grove SELECT COUNT(*) as CountGrove FROM Customer WHERE city = ‘Grove’ • Example 3: Sum all Balance from all Customers SELECT SUM(Balance) as TotalBalance FROM Customer • Example 4: Sum all Balance from all Customers for those who a CreditLimit of $5,000 SELECT SUM(Balance) as TotalBalance FROM Customer WHERE CreditLimit=5000

Non-Graded Exercise • Count all the products from Part table • Count all the products from Part table whose Class is either ‘AP’ or ‘SG’ • Give the Total for the Quantity On Hand from Part table • Give the Sum or Total for the Quoted Price from Orderline table • Give the Sum or Total for the Quoted Price from Orderline table whose Quoted Price is above $400

Subqueries • Subquery: inner query • Subquery is evaluated first • Outer query is evaluated after the subquery

Using Subquery • Example 1: Select orders where whose parts/products are from Warehouse No. 3 SELECT Ordernum FROM Orderline WHERE Partnum IN (SELECT Partnum FROM Part WHERE Warehouse = ‘3’)

Grouping • Create groups of records that share a common characteristic • GROUP BY clause indicates grouping in SQL • HAVING clause is to groups what the WHERE clause is to rows

Using GROUP BY • Example 1: Count how many customers per Sales Representative SELECT Repnum, COUNT(*) as TotalCustomersPerRep FROM Customer GROUP BY Repnum • Example 2: Get the Total of how much Quantity on Hand per Class of all the products SELECT Class, SUM(OnHand) as TotalPerClass FROM Part GROUP BY Class

Using HAVING • Example 2: Get the Total of how much Quantity on Hand per Class of all products that have Quantity on hand above 70 SELECT Class, SUM(OnHand) as TotalPerClass FROM Part GROUP BY Class HAVING SUM(OnHand) > 70

Non-Graded Exercise • Using subquery show orders from Orderline table that has a class of ‘AP’ in Part table • Count all customers from Customer table per City. • Sum all Quantity on Hand from Part table per Warehouse Number. • Display the Sum of Quantity on Hand from Part table per Warehouse Number that has Total Quantity on hand above 100.

Concepts of Database Management Seventh Edition