Beginning SQL

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ALTER TABLE Attendance ADD CONSTRAINT attend_loc_fk FOREIGN KEY (LocationId) REFERENCES Location(LocationId); The Attendance table is the one being altered; the FOREIGN KEY constraint doesn’t affect the Location table. This constraint, for example, is named attend_loc_fk, a mixture of the two tables involved in the relationship, where fk denotes its status as a foreign key. You can name your constraints anything you like; just make sure the name is something that identifies the relationship between tables. Finally, the statement specifies the table and the column or columns being referenced. The following <strong>SQL</strong> adds a second FOREIGN KEY constraint to the Attendance table, this time for the relationship between the Attendance and MemberDetails tables: ALTER TABLE Attendance ADD CONSTRAINT attend_memdet_fk FOREIGN KEY (MemberId) REFERENCES MemberDetails(MemberId); The next table that contains a foreign key is the FavCategory table, but defining that relationship is one of the exercise questions at the end of the chapter. That leaves just one more relationship to define: between the Category and Film tables. The Category table is the primary table to which the Films table links. The link is between the CategoryId columns present in both tables. The following code formally defines this relationship: ALTER TABLE Films ADD CONSTRAINT films_cat_fk FOREIGN KEY (CategoryId) REFERENCES Category(CategoryId); That completes the changes to the database. Innumerable ways to improve a database exist, and these depend on how you intend to use the database. Apart from the index on the MemberDetails table’s FirstName and LastName fields, you didn’t create any new indexes. If in live use you find that some queries take too long to return results, simply review the database structure again and look at changing tables or adding an index to speed things up. Quite a lot of RDBMSs have tools that help monitor performance and tweak settings to ensure the best possible results. Now that you can design a relatively complex normalized database, complete with constraints and primary and foreign keys, here are some things to keep in mind any time you design or modify a database. Tips for Designing a Better Database Advanced Database Design Keeping the following subjects in mind helps ensure that your database design and updates go smoothly. ❑ Don’t design a database that copes with the norm. Tempting as it is to design a database that covers most situations, doing so is dangerous. The unexpected happens just when you least expect it, so make sure you design your database to cover all situations that could arise, or at least ensure that it can cope with the unusual situations. Even if a client tells you not to worry about the possibility of two people attempting to reserve the same holiday cottage at the same time, assume that it will happen. 153
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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
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Figure 1-1 Why and When to Use a Da
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Databases are great at dealing with
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The SQL language is actually fairly
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you wish, and the database system d
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A keyword is a word that has some m
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Introduction to SQL A perfectly val
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Data Type Description Storage Used
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The char and varchar data types use
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Most RDBMSs handle the most common
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To add a new column, use the basic
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Now that you know what you want to
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❑ Meeting date 2 ❑ Location 2
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Generally speaking, picking a data
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example, the MemberId field links t
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Depending on which RDBMS you’re u
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The FilmCategory table is very smal
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2 Entering Information The last cha
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like this: INSERT INTO Category VAL
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Inserting Data into the Case Study
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The WHERE Clause So far you’ve se
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Try It Out Using Logical Operators
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Exercises 1. Three new members have
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Chapter 3 54 MemberId FirstName 1 K
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Chapter 3 The results are as follow
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Chapter 3 The results to this query
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Chapter 3 FavCategory (CategoryId,
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Chapter 3 Logical Operators and Ope
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Chapter 3 The statement returns the
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Chapter 3 NOT Operator Examples thu
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Chapter 3 2. Using the following SQ
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Chapter 3 When you execute the quer
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Chapter 3 Now that you’re acquain
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Chapter 3 It’s as simple as that!
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Chapter 3 76 YearReleased 1947 1967
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Chapter 3 78 FilmName Rating Gone w
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Chapter 3 2. Add a WHERE clause to
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Chapter 3 Executing this SQL provid
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Chapter 3 84 FullName First name is
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Chapter 3 86 FullName First name is
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Chapter 3 Even though DateOfBirth i
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Chapter 3 Member Name The member is
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Chapter 3 92 The preceding SQL prod
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Chapter 3 94 ❑ Category ❑ FavCa
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Chapter 3 96 You’re one step furt
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Chapter 3 98 FirstName LastName Cat
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Chapter 3 This time, you achieve mo
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Chapter 3 SQL Is Set-Based 102 You
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Chapter 3 104 Category MemberId Thr
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Chapter 3 106 You should see the fo
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Chapter 3 The overlapping portions
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Chapter 3 110 More than one conditi
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Chapter 3 112 Next, link the Member
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Chapter 3 114 FirstName LastName Da
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Chapter 3 ❑ The slightly tricky t
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Chapter 4 normalization can make da
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Chapter 4 120 Field Name Data Type
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Chapter 4 122 The Street, City, and
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Chapter 4 MySQL versions prior to 5
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Chapter 4 126 Except for IBM’s DB
Page 296: Chapter 4 128 You can add more than
Page 300: Chapter 4 Try It Out Adding a CHECK
Page 304: Chapter 4 Obviously, if the table i
Page 308: Chapter 4 134 Drop the MoreHolidayB
Page 312: Chapter 4 136 If you want to return
Page 316: Chapter 4 If you’re using IBM DB2
Page 320: Chapter 4 140 index helps speed up
Page 324: Chapter 4 142 The results you get m
Page 328: Chapter 4 144 The results of the qu
Page 332: Chapter 4 146 Remember, IBM DB2 doe
Page 336: Chapter 4 148 UPDATE Films SET Film
Page 340: Chapter 4 150 Finally, you do the s
Page 344: Chapter 4 152 SELECT * FROM MemberD
Page 350: ❑ You learned the importance of e
Page 356: Chapter 5 158 Function Operator Mul
Page 360: Chapter 5 Consider the following SQ
Page 364: Chapter 5 The SQRT() Function The S
Page 368: Chapter 5 164 chairperson now also
Page 372: Chapter 5 The FLOOR() Function The
Page 376: Chapter 5 DVDPrice ROUND(DVDPrice,1
Page 380: Chapter 5 Note that, as with all th
Page 384: Chapter 5 The TRIM() Functions Trim
Page 388: Chapter 5 174 In Oracle and IBM’s
Page 392: 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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