Queries: Part 1 of 2 IS240 DBMS. Topics. Lecture # Four Questions to Create a Query. Why do we Need Queries. Organization.

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1 Queries: Part 1 of 2 IS240 DBMS Lecture # M. E. Kabay, PhD, CISSP-ISSMP Assoc. Prof. Information Assurance School of Business & Management, Norwich University mailto:mkabay@norwich.edu V: opics Why do we Need Queries our Questions to Create a Query Query By Example & SQL Boolean Algebra DeMorgan s Law SQL Server Views Simple Computations SQL Differences Groups and Subtotals Where (Detail) v Having (Group) Student Databases from Website HOMEWORK 1 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 2 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. Why do we Need Queries Natural languages (English) are too vague With complex questions, it can be hard to verify that the question was interpreted correctly, and that the answer we received is truly correct. Consider C the question: Who are our best customers? We need a query system with more structure We need a standardized system so users and developers can learn one method that works on any (most) systems. Query By Example (QBE) SQL our Questions to Create a Query What output do you want to see? What do you already know (or what constraints are given)? What tables are involved? How are the tables joined together? th 3 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 4 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. ables ganization Supplier Contact der derid derdate ReceiveDate Shipping City City State AreaCode Population1990 Population1980 Country Latitude Longitude Merchandise der derdate ReceiveDate Shipping deritem derid ID Employee Last irst axpayerid DateHired DateReleased deritem Quantity Registration ID Registered ListPrice Photo Sale SaleDate CustomerID Salesax Merchandise Description QuantityOnHand ListPrice Sale ID Customer CustomerID irst Last SaleItem Quantity Single table Constraints Computations Groups/Subtotals Multiple ables 5 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 6 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved.

2 Sample Questions Query04_01 Query By Example & SQL List all animals with yellow in their color. List all dogs with yellow in their color born after 6/1/04. List all merchandise for cats with a list price greater than $10. List all dogs who are male and registered or who were born before 6/1/04 and have white in their color. What is the average sale price of all animals? What is the total cost we paid for all animals? List the top 10 customers and total amount they spent. How many cats are in the animal list? Count the number of animals in each category. List the CustomerID of everyone who bought something between 4/1/04 and 5/31/04. List the first name and phone of every customer who bought something between 4/1/04 and 5/31/04. List the last name and phone of anyone who bought a registered white cat between 6/1/04 and 12/31/04. Which employee has sold the most items? What tables? ID ield able ID What to see? SELECID,,, ROM WHERE ( LIKE %Yellow% ); List all animals with yellow in their color What conditions? Like %Yellow% 7 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 8 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. Basic SQL SELEC ORDER BY SELEC columns What do you want to see? ROM tables What tables are involved? JOIN conditions How are the tables joined? WHERE criteria What are the constraints? SELEC columns ROM tables JOIN join columns WHERE conditions ORDER BY columns (ASC DESC) ID ield able SELEC,, ROM ORDER BY, ; Ascending Ascending hy Bird African Grey Bird Canary Debbie Bird Cockatiel Bird Cockatiel erry Bird Lovebird Bird Other Charles Bird Parakeet Curtis Bird Parakeet Ruby Bird Parakeet Sandy Bird Parrot Hoyt Bird Parrot Bird Parrot 9 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 10 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. DISINC Query04_02 Constraints: And SELEC ROM ; ish ish ish ish... SELEC DISINC ROM ; Bird ish Mammal Reptile Spider List all dogs with yellow in their color born after 6/1/04. ID SELECID,, ROM WHERE ((= ) AND ( Like %Yellow% ) AND (> 01-Jun-2004 )); ield ID able '' > 01-Jun-2004 Like %Yellow% 11 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 12 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved.

3 Boolean Algebra And: Both must be true. : Either one is true. Not: Reverse the value. a b a AND b a OR b a = 3 b = -1 c = 2 (a > 4) And (b < 0) (a > 4) (b < 0) NO (b < 0) Boolean Algebra he result is affected by the order of the operations. Parentheses indicate that an operation should be performed first. With no parentheses, operations are performed left-to-right. Always use parentheses so other people can read and understand your query. It will also help you when you come back to one of your own queries later. a = 3 b = -1 c = 2 ( (a > 4) AND (b < 0) ) OR (c > 1) (a > 4) AND ( (b < 0) OR (c > 1) ) 13 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 14 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. DeMorgan s Law Example Customer:"I want to look at a cat, but I don t want any cats that are registered or that have red in their color." ID SELEC ID,, Registered, ROM WHERE (= ) AND NO ((Registered is NO NULL) OR ( LIKE %Red% )). ield ID Registered able Is Null Not Like %Red% 15 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. DeMorgan s Law Negation of clauses Not (A And B) becomes Not A Not B Not (A B) becomes Not A And Not B Customer:"I want to look at a cat, but I don t want any cats that are registered or that have red in their color." 16 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. CA: Registered=ASC =Black NO ((Registered is NO NULL) OR ( LIKE %Red% )) or not (Registered is NULL) AND NO ( LIKE %Red% ) not and Query04_03 Conditions: AND, OR SELEC ID,,, Registered,, ROM WHERE (( = ) AND ( ( (= Male ) AND (Registered Is Not Null) ) OR ( (< 01-Jun-2004 ) AND ( Like %White% ) ) ) ); ID List all dogs who are male and registered or who were born before 6/1/2004 and have white in their color. ield ID Registered able Male Is Not Null < 01-Jun-2004 Like %White% Useful Where Conditions Comparisons Examples Operators <, =, >, <>, BEWEEN, LIKE, IN Numbers AccountBalance > 200 ext Simple Pattern match one Pattern match any Dates Missing Data Negation Sets > Jones License LIKE A 82_ LIKE J% SaleDate BEWEEN 15-Aug-2004 AND 31-Aug-2004 City IS NULL IS NO NULL IN (,, Hamster ) 17 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 18 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved.

4 SQL in MS-ACCESS View Design View Simple Computations Basic computations (+ - /) can be performed on numeric data. he new display column should be given a meaningful name. SaleItem(derID,,, Quantity) View SQL View Select derid,,, Quantity, Quantity As Extended rom SaleItem; derid Price Quantity Extended Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 20 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. Computations: Aggregation- -Avg What is the average sale price of all animals? SELEC Avg() AS AvgOf ROM Sale; Sale ID ield able otal Sale Avg Sum Avg Min Max Count StDev or StdDev Var Computations (Math Operators) What is the total value of the order for 22? Use any common math operators on numeric data. Operate on data in one row at a time. deritem Quantity SELEC Sum(Quantity) AS derotal ROM deritem WHERE (=22); ield derotal: Quantity able deritem deritem otal =22 derotal Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 22 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. SQL Differences ask Access SQL Server acle Strings Concatenation Length Upper case Lower case Partial string & & L Len(L) UCase(L) LCase(L) MID(L,2,3) + + L Length(L) Upper(L) Lower(L) Substring(L,2,3) L LENGH(L) UPPER(L) LOWER(L) SUBSR(L,2,3) Dates oday Month Day Date( ), ime( ), Now( ) Month(myDate) Day(myDate) D GetDate() Date(month, mydate) DatePart(day, t(d mydate) SYSDAE RUNC(myDate, mm ) RUNC (mydate, dd ) Year Date arithmetic Year(myDate) DateAdd DateDiff DatePart(year, mydate) DateAdd DateDiff ormatting ormat(item, format) Str(item, length, decimal) Cast, Convert Numbers Math functions Cos, Sin, an, Sqrt Cos, Sin, an, Sqrt Exponentiation 2 ^ 3 Power(2, 3) Aggregation Min, Max, Sum, Count, Min, Max, Sum, Count, Statistics Avg StDev, Var Avg, StDev, Var, LinReqSlope, Correlation RUNC (mydate, yyyy ) ADD_MONHS MONHS_BEWEEN LAS_DAY O_CHAR(item, format) O_DAE(item, format) COS, SIN, AN, SQR POWER(2,3) MIN, MAX, SUM, COUN, AVG, SDDEV, VARIANCE, REGR, CORR Subtotals (Where) ID How many cats are in the list? SELEC Count(ID) AS CountOfID ROM WHERE ( = ); ield ID able otal Count Where 23 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 24 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved.

5 Groups and Subtotals Count the number of animals in each category. You could type in each WHERE clause, but that is slow. And you would have to know all of the values. ID SELEC, Count(ID) AS CountOfID ROM GROUP BY ORDER BY Count(ID) DESC; ield ID able otal Group By Count CountOfID Bird 15 ish 14 Reptile 6 Mammal 6 Spider 3 Conditions on otals (Having) Count number of s in each, but list only if more than 10 in that. ID ield ID able otal Group By Count >10 SELEC, Count(ID) AS CountOfID ROM GROUP BY HAVING Count(ID) > 10 ORDER BY Count(ID) DESC; CountOfID Bird 15 ish Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 26 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. Where (Detail) v Having (Group) Count s born after 6/1/2004 in each, but list only if more than 10 in that. Student Databases from Website ID SELEC, Count(ID) AS CountOfID ROM WHERE > 01-Jun-2004 GROUP BY HAVING Count(ID) > 10 ORDER BY Count(ID) DESC; ield ID able otal Group By Count Where >10 > 01-Jun-2004 CountOfID Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 28 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. HOMEWORK REQUIRED By Sun 28 eb 2010 at 23:59 Study Chapter 4 pp thoroughly using SQ3R Answer Review Questions 1-12 for yourself to be sure they all make sense to you and you can easily answer them later in quizzes Download the PetStore2000.mdb or PetStore2002.mdb file (as appropriate for your system) from Jerry Post s site Create SQL code and the records you find to Ch 4 Sally s Pet Store exercises 1-7 (there s no way to learn SQL without actually using it). HOMEWORK OPIONAL By Sun 28 eb 2010 at 23:59 or extra credit, answer any of the questions in Rolling hunder Bicycles #26-35 Corner Med # Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved. 30 Copyright 2010 Jerry Post & M. E. Kabay. All rights reserved.