Beginning SQL

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9 Advanced Queries In database programming, you’ll find that roughly 95 percent of queries are fairly straightforward and are just a matter of working out what columns are required and including a simple WHERE clause to filter out the unwanted results. This chapter is all about how to tackle the other 5 percent, which are difficult and complex queries. This chapter also presents a number of questions and examines how to write the <strong>SQL</strong> to answer them. Specifically, this chapter covers the following: ❑ Tackling complex queries ❑ Formulating precise SELECT column lists and FROM clauses ❑ Writing ruthlessly efficient queries Before getting into the specifics of the chapter, you need to begin by making some additions to the Film Club database. Updating the Database In order to give more scope for tricky queries and avoid repeating examples from previous chapters, this chapter extends the Film Club database and adds some new tables and data. Imagine that the film club chairperson wants to sell DVDs to members; the film club will employ salespeople to contact members and sell them DVDs. Therefore, you want to store details of the salespeople, details of orders taken, and details of what each order contains. In order to do this, you need to create three new tables (Orders, OrderItems, and SalesPerson), as shown in Figure 9-1:
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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
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Chapter 4 128 You can add more than
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Chapter 4 Try It Out Adding a CHECK
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Chapter 4 Obviously, if the table i
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Chapter 4 134 Drop the MoreHolidayB
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Chapter 4 136 If you want to return
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Chapter 4 If you’re using IBM DB2
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Chapter 4 140 index helps speed up
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Chapter 4 142 The results you get m
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Chapter 4 144 The results of the qu
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Chapter 4 146 Remember, IBM DB2 doe
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Chapter 4 148 UPDATE Films SET Film
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Chapter 4 150 Finally, you do the s
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Chapter 4 152 SELECT * FROM MemberD
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Chapter 4 ❑ Choose meaningful nam
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5 Manipulating Data In Chapter 3, y
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The results of this query are as fo
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You can raise a number to any power
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To demonstrate the sort of results
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The CEILING() Function The CEILING(
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ased on the digits after the decima
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The SUBSTRING() function works at t
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LastName UPPER(LastName) LOWER(Last
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The LENGTH() function takes just on
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LastName LOWER(SUBSTRING(LastName,1
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FirstName DIFFERENCE(FirstName, ‘
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Converting Different Data Types Thi
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CREATE Table MyTable(FirstColumn in
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The COALESCE() Function The COALESC
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Ideally, this first argument is the
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LocationId Street City State 1 Main
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6 Grouping and Aggregating Data So
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Running the query, complete with a
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MemberId Street City State 11 Newis
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Executing the SQL returns seven dis
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For example, the following code add
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Running the query gives the answer
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SELECT MAX(LastName), MIN(LastName)
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immediately after the GROUP BY stat
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Executing the final SQL provides th
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Chapter 7 The INNER JOIN links the
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Chapter 7 FilmName FirstName LastNa
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Chapter 7 212 As mentioned, that wo
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Chapter 7 Category Street Romance T
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Chapter 7 216 MD1.First MD1.Last MD
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Chapter 7 SELECT MD1.MemberId, MD1.
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Chapter 7 220 SELECT Category, Film
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Chapter 7 222 Location.Street Membe
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Chapter 7 224 Category MemberId War
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Chapter 7 Look at the results that
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Chapter 7 228 The Maltese Poodle 8
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Chapter 7 230 9 10 11 12 13 14 15 1
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Chapter 7 232 On Golden Puddle 1967
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8 Queries within Queries This chapt
Page 514: There are no films with a value in
Page 518: The error wording depends on the da
Page 522: Now execute the query. You receive
Page 526: The query provides the following re
Page 530: If you execute this query, you can
Page 534: To obtain the same results as you w
Page 538: MemberId 1 10 14 6 5 8 7 11 15 4 13
Page 542: Now NOT EXISTS returns true, and as
Page 546: This is the same as the query just
Page 550: clause specifying that the film’s
Page 554: 4. Next, quickly double-check a few
Page 558: Now that you’ve confirmed that th
Page 562: Summary Queries within Queries This
Page 570: FOREIGN KEY (OrderId) REFERENCES Or
Page 574: INSERT INTO Orders(OrderId, MemberI
Page 578: INSERT INTO OrderItems(OrderId,Film
Page 582: A more complex question could be,
Page 586: Advanced Queries What you really wa
Page 590: FirstName and LastName. You need to
Page 594: 2. The film club chairperson also w
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Page 602: GROUP BY SalesPerson.SalesPersonId,
Page 606: Executing the preceding SQL creates
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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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