Beginning SQL

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example, the MemberId field links the member in the Attendance table with their full details in the MemberDetails table. You have a primary key for the MemberDetails table, MemberId, but what about for the Attendance table? The Attendance table has a unique identifier — the combination of MeetingDate and MemberId, because it’s not possible for a member to attend the same meeting twice! Therefore, using those two columns in combination to provide unique identification is safe. This provides a nice segue to the second point about primary keys: They don’t have to be composed of just one column, as in the case of the Attendance table. If you wanted to, you could create a unique meeting ID, but in this situation a unique meeting ID is not necessary and wastes storage space. If speed of data retrieval were a vital issue, you might consider using a primary key, but most of the time it’s not necessary. A primary key simply involves having a column to store a unique value and then generating that value. However, most RDBMSs also allow you to specify a column as a primary key, and in doing so, the RDBMS manages data entry. In particular, you can apply constraints to exactly what data can go in the field. For example, constraints prevent you from having two records with the same primary key value. After all, the point of a primary key is that it’s unique. Chapter 4 delves deeper into the more advanced and tricky aspects of primary keys and constraints, but now you have the requisite knowledge to create your first full-fledged database. The database you create in the next section is the one you use throughout the book. Creating the Example Database The example database continues the previous discussion of the Film Club database. You need to create a database to store the tables. You can call your database something like Film Club, though for the purposes of this book, the database’s name is not important. Appendix B has all the specifics needed for creating a blank example database in either Access, SQL Server, DB2, MySQL, or Oracle. Once you’ve created the Film Club database, it’s time to start populating it with tables. The basic premise is that you’re running a film club, and you want a database that stores the following information: ❑ Club member details, such as name, address, date of birth, date they joined, and email address ❑ Meeting attendance details ❑ Film details ❑ Members’ film category preferences Introduction to SQL These are the requirements now, though later in the book, you develop and expand the database. You’ve already established the club membership’s details, but notice the additional fields in the following table: 35
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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
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Contents xii Re-examining NULL 180
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Contents Chapter 11: Transactions 3
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Contents xvi How Do You Do It? 357
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Introduction Data, data, data! Data
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By the time you’ve completed Chap
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Once you download the code, just de
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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 78: Introduction to SQL A perfectly val
Page 82: Data Type Description Storage Used
Page 86: The char and varchar data types use
Page 90: Most RDBMSs handle the most common
Page 94: To add a new column, use the basic
Page 98: Now that you know what you want to
Page 102: ❑ Meeting date 2 ❑ Location 2
Page 106: Generally speaking, picking a data
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
Page 128: Chapter 2 44 Member First Last Date
Page 132: Chapter 2 46 Now Steve’s record l
Page 136: Chapter 2 This would work fine with
Page 140: Chapter 2 If you want to delete all
Page 146: 3 Extracting Information So far you
Page 150: Returning Only Distinct Rows If you
Page 154: The good news is that everything yo
Page 158: 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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