Beginning SQL

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Introduction to SQL A perfectly valid question to ask is, “Why have different data types?” Why not just treat everything as text? The main reason is efficiency. The amount of storage space and the speed of access improve when the database knows what sort of data it’s dealing with. For example, the number 243787452 can be stored in as little as 4 bytes of computer memory. Storing the same number as text takes 9 bytes of memory for the character data. In addition, the data type determines what the RDBMS expects users to do with the data. If you have numerical data, then 123 + 123 calculates as addition with the answer being 246. If it were text data, the RDBMS would interpret the plus sign as meaning that you want to join the two character strings together to form 123123. So what are the various data types available? Unfortunately, data type varies among RDBMSs. Added to this conundrum is the problem that while the ANSI SQL standards such as SQL-92, SQL-99, and SQL- 2003 define standards for data types, they are far from fully and universally implemented by the various RDBMS manufacturers. However, all is not lost. There’s enough support of the standards for the purposes of this book. Once you have a handle on the basic ANSI SQL data types, researching the data types that your particular RDBMS uses is fairly easy. You can then use them in addition to the data types examined here. The following table contains a subset of the more commonly used ANSI SQL data types and the name of the same data type in other RDBMSs such as SQL Server, IBM DB2, and so on. ANSI SQL MS Access SQL Server 2000 IBM DB2 MySQL Oracle 10 Character char char char char char Character varying varchar varchar varchar varchar varchar National character char nchar graphic char nchar National character varchar nvarchar vargraphic varchar nvarchar varying Integer number (long int int int int integer) Smallint number smallint smallint smallint smallint (integer) Real number real real real real (double) Decimal number decimal decimal decimal decimal (decimal) Date date datetime date date date Time time datetime time time date 19
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Beginning SQL Paul Wilton and John
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Beginning SQL Paul Wilton and John
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About the Authors Paul Wilton After
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Paul Wilton: With lots of love to m
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Contents x Selecting Correct Data T
Page 28: Contents xii Re-examining NULL 180
Page 32: Contents Chapter 11: Transactions 3
Page 36: Contents xvi How Do You Do It? 357
Page 42: Introduction Data, data, data! Data
Page 46: By the time you’ve completed Chap
Page 50: Once you download the code, just de
Page 54: 1 Introduction to SQL A nice, gentl
Page 58: Figure 1-1 Why and When to Use a Da
Page 62: Databases are great at dealing with
Page 66: The SQL language is actually fairly
Page 70: you wish, and the database system d
Page 74: A keyword is a word that has some m
Page 80: Chapter 1 20 Although this table in
Page 84: Chapter 1 Characters 22 When you wa
Page 88: Chapter 1 Look at an example to mak
Page 92: Chapter 1 The following SQL creates
Page 96: Chapter 1 You should now know enoug
Page 100: Chapter 1 30 Date of Date of Meetin
Page 104: Chapter 1 The Attendance table coul
Page 108: Chapter 1 34 to thousands of member
Page 112: Chapter 1 36 Field Name Data Type N
Page 116: Chapter 1 38 Finally, you need to a
Page 120: Chapter 1 ❑ Databases are part of
Page 124: Chapter 2 42 CategoryId Category 1
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Chapter 2 44 Member First Last Date
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Chapter 2 46 Now Steve’s record l
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Chapter 2 This would work fine with
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Chapter 2 If you want to delete all
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3 Extracting Information So far you
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Returning Only Distinct Rows If you
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The good news is that everything yo
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MemberDetails (MemberId, FirstName,
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MemberDetails table, the columns Fi
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State DateOfJoining New State 2005-
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It simply tells the database system
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The BETWEEN operator functions exac
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The final condition required is a c
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In some database systems, the LIKE
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The second query is a negative, in
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Because both conditions (YearReleas
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YearReleased 1984 1980 1977 1975 19
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First, the database system orders t
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LastName FirstName DateOfBirth Nigh
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The preceding SQL returns the follo
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If you put square brackets around i
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Finally, if you want to use an alia
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Member Name The member is called Ka
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FilmName YearReleased Rating Sense
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Figure 3-1 The first task when tack
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That’s all well and good, but so
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Category FirstName LastName War Jen
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Extracting Information FirstName La
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If you take this further and join t
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SELECT * FROM FavCategory Figure 3-
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Category MemberId Thriller 5 Thrill
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Remember to add brackets around the
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surprisingly, the MemberDetails tab
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LocationId 2 2 2 2 1 1 1 Figure 3-6
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includes that record. You should al
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FirstName LastName DateOfBirth Jenn
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4 Advanced Database Design This cha
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Date of Date Meeting Did Member Nam
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Now the tables are in second normal
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After changing the database so that
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IBM’s DB2 doesn’t allow you to
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The following code creates a new ta
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If you’re using DB2, the code is
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The NOT NULL constraint prevents th
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In the preceding code, CustomerId i
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Foreign Key Foreign keys are column
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MemberId MeetingDate Street City St
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The third step had you create the p
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The results are ordered because, by
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The index is no longer needed, so d
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WHERE MemberAttended = ‘Y’; DRO
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Primary keys must be unique and can
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Then add the PRIMARY KEY constraint
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( ); FilmId integer NOT NULL, FilmN
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ALTER TABLE Attendance ADD CONSTRAI
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❑ You learned the importance of e
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Chapter 5 158 Function Operator Mul
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Chapter 5 Consider the following SQ
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Chapter 5 The SQRT() Function The S
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Chapter 5 164 chairperson now also
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Chapter 5 The FLOOR() Function The
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Chapter 5 DVDPrice ROUND(DVDPrice,1
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Chapter 5 Note that, as with all th
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Chapter 5 The TRIM() Functions Trim
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Chapter 5 174 In Oracle and IBM’s
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Chapter 5 176 FirstName SOUNDEX(Fir
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Chapter 5 Date Functions 178 Someti
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Chapter 5 The syntax for the CAST()
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Chapter 5 NULLs and Strings 182 NUL
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Chapter 5 184 SELECT FirstName, Las
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Chapter 5 186 This SQL copies over
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Chapter 5 You also learned that mat
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Chapter 6 190 Begin by looking at h
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Chapter 6 This section covers queri
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Chapter 6 194 This query gives the
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Chapter 6 You’re almost there. Yo
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Chapter 6 the database even though
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Chapter 6 SELECT Category, AVG(DVDP
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Chapter 6 Try It Out Selecting Data
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Chapter 6 SELECT Category, COUNT(Fa
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7 Selecting Data from Different Tab
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Selecting Data from Different Table
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Note that MS Access insists that yo
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City State Orange Town New State Wi
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SELECT FM1.FilmName FROM Films AS F
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Selecting Data from Different Table
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effects of any WHERE clause. There
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Now re-execute the query. You get a
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the category list and a list of whi
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Category FirstName LastName Horror
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You can join the results from two o
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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function and the query still works,
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Summary Selecting Data from Differe
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Chapter 8 A WHERE clause is added t
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Chapter 8 238 FilmName PlotSummary
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Chapter 8 If you think that your jo
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Chapter 8 In the query, the Categor
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Chapter 8 244 There is one area in
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Chapter 8 246 SELECT FirstName, Las
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Chapter 8 248 The subquery (SELECT
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Chapter 8 250 Notice the use of the
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Chapter 8 4. You should receive the
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Chapter 8 254 This inner query retu
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Chapter 8 It’s quite important no
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Chapter 8 258 To tackle this query,
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Chapter 8 260 Now you need to find
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9 Advanced Queries In database prog
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FOREIGN KEY (OrderId) REFERENCES Or
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INSERT INTO Orders(OrderId, MemberI
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INSERT INTO OrderItems(OrderId,Film
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A more complex question could be,
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Advanced Queries What you really wa
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FirstName and LastName. You need to
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2. The film club chairperson also w
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Executing the preceding query provi
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GROUP BY SalesPerson.SalesPersonId,
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Executing the preceding SQL creates
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❑ Use IN with your subqueries. Wh
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10 Views Views, as the name implies
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Try It Out Building a View 1. The p
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FROM dbo.MemberDetails INNER JOIN d
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For example, you might want a list
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However, if you take the case of Me
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However, someone writes a query tha
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Summary As you learned, views are l
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Chapter 11 The information that fol
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Chapter 11 This SQL adds formats (d
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Chapter 11 TRANSACTION statement is
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Chapter 11 Additionally, if a DBMS
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Chapter 11 ROLLBACK TRANSACTION 310
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Chapter 11 Transaction Logs 312 How
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Chapter 11 Database There are perfe
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Chapter 11 In order to find and fix
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Chapter 11 When discussing locking,
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Chapter 11 Usually, the default iso
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Chapter 11 From Sue’s perspective
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Chapter 11 5. At this point, you ne
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12 SQL Security In today’s world,
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Setting up security begins with cre
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ALTER USER username options ALTER U
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In Figure 12-3, three different gro
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How It Works After you run this sta
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check constraints can be used in a
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You could then give SELECT privileg
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Limitations on Views Views are by t
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GRANT SELECT (NAME, SSN, SALARY) ON
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Betsey also grants privileges to Ji
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The CASCADE option tells the DBMS t
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13 Database Tuning SQL is a languag
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Perhaps this doesn’t sound remote
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When an application asks for data f
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The point of all the discussion of
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How Do You Do It? And herein lies t
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The slots are often implemented as
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On the other hand, an index on a tr
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Tuning Tips The following list cont
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Database Tuning Exercises 1. Create
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Appendix A Exercise 2 Solution 368
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Appendix A ( 8, ‘Jack’, ‘John
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Appendix A ZipCode, Email, DateOfJo
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Appendix A Exercise 3 Solution Firs
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Appendix A 376 Figure A-1 ISBN is a
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Appendix A Chapter 5 Exercise 1 Sol
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Appendix A 380 You might receive sl
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Appendix A 382 You should use the f
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Appendix A Your answer may differ,
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Appendix A WHERE (SELECT COUNT(*) f
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Appendix A Exercise 2 Solution CREA
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Appendix A Chapter 13 Exercise 1 So
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Appendix B 392 Click the database i
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Appendix B 394 Click Install to beg
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Appendix B 396 Select the Detailed
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Appendix B 398 Leave it at the defa
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Appendix B 400 Having entered your
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Appendix B 402 Figure B-20 The inst
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Appendix B 404 At the very top of t
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Appendix B 406 Having done that, ma
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Appendix B 408 Figure B-30 MyTable
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Appendix B 410 Figure B-32 Click Ne
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Appendix B 412 Click Next to contin
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Appendix B 414 Click OK to clear th
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Appendix B If you’re ready and ha
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Appendix B 418 You can also enter a
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Appendix B 420 Figure B-49 The Film
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Appendix B 422 Now you need to inse
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Appendix B 424 In Access it’s not
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Appendix B 426 Figure B-56 You need
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Appendix B 428 Then click the Run i
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Appendix B 430 The next screen (see
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Appendix B 432 On the next screen,
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Appendix B 434 Click Next to procee
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Appendix B 436 Figure B-72 The huge
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Appendix B 438 Figure B-74 Notice t
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Appendix B 440 Figure B-76 The Obje
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Appendix B 442 Figure B-78 Chapter
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Appendix B You don’t need MyTable
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Appendix B 446 Figure B-82 To begin
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Appendix B Using Oracle’s SQL*Plu
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Appendix B 450 Figure B-87 Another
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Appendix C Category Table The follo
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Appendix C 454 ( 3, ‘Sandra’,
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Appendix C 456 ZipCode, Email, Date
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Appendix C DateOfJoining ) VALUES (
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Appendix C 460 VALUES ( 1, 3 ); INS
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Appendix C VALUES ( 5, 3 ); INSERT
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Appendix C 464 3 ); INSERT INTO Fil
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Appendix C 5, 6 ); INSERT INTO Film
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Appendix C 468 5 ); INSERT INTO Att
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Appendix C Oracle 470 To save some
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Appendix C 472 LocationId, MeetingD
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Symbols + (addition operator), 82,
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BEGIN TRANSACTION statement, 306, 3
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SERIALIZABLE statement, 318 SET TRA
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data types brackets, 25 categories,
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Oracle concatenation, 85-88 configu
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error messages debugging, 26 subque
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concatenation, 85-88 data type comp
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primary keys database creation exam
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concurrent connection selection, 39
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passwords group access, 333 IBM ins
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ROLLBACK statement, 307-308 ROLLBAC
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REPEATABLE READ, 319 REVOKE, 344-34
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telephone numbers, data type select
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historical, data selection, 90-94 N
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Beginning SQL

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