Beginning SQL

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Perhaps this doesn’t sound remotely like application tuning, but the application runs on machines. If the machines don’t support the application, you are never going to tune it enough to make a difference! Database Files Client server DBMSs (as opposed to file server DBMSs such as Microsoft Access) often allow you to distribute the database across many different hard disks. The objective is to split the database into files, with each disk holding a single file containing one or a set of tables, or even sets of indexes. By splitting the database up like this, you can get the physical input/output (I/O) distributed across many electronic channels, you get the disks accessing their pieces of the data in parallel so that the data from one disk can be read while the other disks are looking for data being requested, and finally you get cache on each hard drive holding a piece of the database. DBMSs like <strong>SQL</strong> Server and Oracle have tools that allow you to set up complex, time-consuming queries and then watch the physical IO (disk access) to see if you are saturating the data channel(s), in other words transferring the maximum amount of data that the disk is capable of putting out. If this happens, then you have discovered a bottleneck and should consider splitting the database down into more files, one file per hard disk, which means adding hard disks to the system. Correctly implemented, adding hard disks to the system raises the amount of data that can be read out of the database. When the point is reached where the hard disks can feed data faster than the processor can handle it, you have eliminated one bottleneck and can look elsewhere for the next bottleneck. Processors Database Tuning DBMSs are one of the applications that are specifically written to utilize multiprocessor systems. Multiprocessing simply means having more than a single central processing unit (CPU) in the server box. While they are not cheap, adding processors to a database server can in certain circumstances make the database significantly faster. The reason is that queries can be broken down into pieces, and those pieces assigned to different processors. The individual processors handle pulling the indexes for their individual piece of the puzzle, narrowing down the data and finally returning a small data set to a processor that puts all the pieces back together into the original query. Just like breaking the database itself down into files on different hard disks, the net effect is to get parallel processing happening so that the whole process is executed faster. Unfortunately you usually can’t simply pop in an additional processor to upgrade your server. The motherboard has to be designed to hold multiple CPUs before you can do this. Even if you can add a new processor (there is an empty CPU socket), if the machine is old, adding the new processor may be difficult or impossible. Getting your hands on the processor for a five-year-old machine may be difficult, and even if you manage to do so, the slow speed of the processor may make the performance boost less than you might hope for compared to buying a new multi-gigahertz machine. On the other hand, if you can find a processor to pop into your multiprocessor machine, doing so almost certainly would provide some performance increase and would almost assuredly be better than no upgrade at all. If your current database server system has a clock speed of less than 1GHz, and certainly if it is a singleprocessor system with a clock speed of less than 1GHz, moving up to a modern machine (possibly with multiprocessors) would almost assuredly provide large efficiency gains over what you have now. It isn’t cheap, but if the budget allows it, this may go a long way toward speeding up almost any slow database application. 351
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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
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There are no films with a value in
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The error wording depends on the da
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Now execute the query. You receive
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The query provides the following re
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If you execute this query, you can
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To obtain the same results as you w
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MemberId 1 10 14 6 5 8 7 11 15 4 13
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Now NOT EXISTS returns true, and as
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This is the same as the query just
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clause specifying that the film’s
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4. Next, quickly double-check a few
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Now that you’ve confirmed that th
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Summary Queries within Queries This
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Chapter 9 264 Figure 9-1 The SQL ne
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Chapter 9 266 INSERT INTO OrderItem
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Chapter 9 268 VALUES (5,7, 2,’200
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Chapter 9 Now that you’ve added t
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Chapter 9 272 FirstName LastName Mo
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Chapter 9 274 DVDPrice column is in
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Chapter 9 SalesPersonId FirstName L
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Chapter 9 278 SalesPersonId MemberI
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Chapter 9 280 SalesPersonId MemberI
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Chapter 9 282 MemberDetails.FirstNa
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Chapter 9 284 The query would work
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Chapter 9 Exercises 286 Assume that
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Chapter 10 Now that you know what v
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Chapter 10 Types of Views Given tha
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Chapter 10 Perhaps you need to view
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Chapter 10 Figure 10-7 Summary view
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Chapter 10 296 This statement gives
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Chapter 10 The CHECK OPTION plays a
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11 Transactions When you move out o
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Example Data This section creates e
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3. Build a record in the Rentals ta
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The other statement that the ANSI S
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SAVE TRANSACTION Select Update Begi
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Figure 11-5 Begin Transaction Delet
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In spite of all of these performanc
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Shared A shared lock essentially me
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of record locks, the DBMS may decid
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No updates, additions, or deletions
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International Board Manufacturer ha
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contention. You could wrap your new
Page 690: Summary Transactions ensure that us
Page 696: Chapter 12 328 SQL security is cent
Page 700: Chapter 12 Creating User IDs Figure
Page 704: Chapter 12 3. In the SQL window, ty
Page 708: Chapter 12 ❑ You can assign a dif
Page 712: Chapter 12 Privileges Privileges ar
Page 716: Chapter 12 338 You could then give
Page 720: Chapter 12 You might implement this
Page 724: Chapter 12 Another shortcut, using
Page 728: Chapter 12 As you can imagine, givi
Page 732: Chapter 12 The situation gets a lit
Page 736: Chapter 12 Summary Database securit
Page 740: Chapter 13 robust, fault-tolerant m
Page 746: When an application asks for data f
Page 750: The point of all the discussion of
Page 754: How Do You Do It? And herein lies t
Page 758: The slots are often implemented as
Page 762: On the other hand, an index on a tr
Page 766: Tuning Tips The following list cont
Page 770: Database Tuning Exercises 1. Create
Page 776: Appendix A Exercise 2 Solution 368
Page 780: Appendix A ( 8, ‘Jack’, ‘John
Page 784: Appendix A ZipCode, Email, DateOfJo
Page 788: 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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