Beginning SQL

More documents

Recommendations

Info

3 Extracting Information So far you’ve learned how to set up a database and how to insert data into it, so now you can learn how to extract data from your database. Arguably, SQL’s most powerful feature is its ability to extract data, and extracting data can be as simple or complex as you require. You can simply extract data in the same form in which it was entered into the database, or you could query the database and obtain answers to questions that are not obvious from the basic data. In your example database, you can use SQL to find out which meeting locations are most popular, or you could find out which meeting locations are most popular for which film category. It might turn out that Windy Village has a particularly large number of sci-fi fans. If the film club decides to show a film at that location, you would be aware that a sci-fi film is likely to be popular. The ability to ask the database questions and get answers via SQL queries makes SQL so popular and useful. The key to getting data out is the SELECT statement, which in its basic form is very simple and easy to use. However, as you go through this chapter and then the advanced chapters, you see lots of extra options that make the SELECT statement very powerful. Before getting too complicated, however, you need to familiarize yourself with the SELECT statement. The SELECT Statement At its simplest, the SELECT requires you to tell it which columns and from what table you want to obtain data. The basic syntax is as follows: SELECT column1, column2,.....columnx FROM table_name Using the basic syntax, the SQL required to select the MemberId and FirstName columns from all records in the MemberDetails table is SELECT MemberId, FirstName FROM MemberDetails; The order in which you list the columns in the SELECT statement determines the order in which they are returned in the results. The preceding query returns this order:
Page 2:
Beginning SQL Paul Wilton and John
Page 10:
Beginning SQL Paul Wilton and John
Page 14:
About the Authors Paul Wilton After
Page 18:
Paul Wilton: With lots of love to m
Page 24:
Contents x Selecting Correct Data T
Page 28:
Contents xii Re-examining NULL 180
Page 32:
Contents Chapter 11: Transactions 3
Page 36:
Contents xvi How Do You Do It? 357
Page 42:
Introduction Data, data, data! Data
Page 46:
By the time you’ve completed Chap
Page 50:
Once you download the code, just de
Page 54:
1 Introduction to SQL A nice, gentl
Page 58:
Figure 1-1 Why and When to Use a Da
Page 62:
Databases are great at dealing with
Page 66:
The SQL language is actually fairly
Page 70:
you wish, and the database system d
Page 74:
A keyword is a word that has some m
Page 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 110: example, the MemberId field links t
Page 114: Depending on which RDBMS you’re u
Page 118: The FilmCategory table is very smal
Page 122: 2 Entering Information The last cha
Page 126: like this: INSERT INTO Category VAL
Page 130: Inserting Data into the Case Study
Page 134: The WHERE Clause So far you’ve se
Page 138: Try It Out Using Logical Operators
Page 142: Exercises 1. Three new members have
Page 150: Returning Only Distinct Rows If you
Page 154: The good news is that everything yo
Page 158: MemberDetails (MemberId, FirstName,
Page 162: MemberDetails table, the columns Fi
Page 166: State DateOfJoining New State 2005-
Page 170: It simply tells the database system
Page 174: The BETWEEN operator functions exac
Page 178: The final condition required is a c
Page 182: In some database systems, the LIKE
Page 186: The second query is a negative, in
Page 190: Because both conditions (YearReleas
Page 194:
YearReleased 1984 1980 1977 1975 19
Page 198:
First, the database system orders t
Page 202:
LastName FirstName DateOfBirth Nigh
Page 206:
The preceding SQL returns the follo
Page 210:
If you put square brackets around i
Page 214:
Finally, if you want to use an alia
Page 218:
Member Name The member is called Ka
Page 222:
FilmName YearReleased Rating Sense
Page 226:
Figure 3-1 The first task when tack
Page 230:
That’s all well and good, but so
Page 234:
Category FirstName LastName War Jen
Page 238:
Extracting Information FirstName La
Page 242:
If you take this further and join t
Page 246:
SELECT * FROM FavCategory Figure 3-
Page 250:
Category MemberId Thriller 5 Thrill
Page 254:
Remember to add brackets around the
Page 258:
surprisingly, the MemberDetails tab
Page 262:
LocationId 2 2 2 2 1 1 1 Figure 3-6
Page 266:
includes that record. You should al
Page 270:
FirstName LastName DateOfBirth Jenn
Page 274:
4 Advanced Database Design This cha
Page 278:
Date of Date Meeting Did Member Nam
Page 282:
Now the tables are in second normal
Page 286:
After changing the database so that
Page 290:
IBM’s DB2 doesn’t allow you to
Page 294:
The following code creates a new ta
Page 298:
If you’re using DB2, the code is
Page 302:
The NOT NULL constraint prevents th
Page 306:
In the preceding code, CustomerId i
Page 310:
Foreign Key Foreign keys are column
Page 314:
MemberId MeetingDate Street City St
Page 318:
The third step had you create the p
Page 322:
The results are ordered because, by
Page 326:
The index is no longer needed, so d
Page 330:
WHERE MemberAttended = ‘Y’; DRO
Page 334:
Primary keys must be unique and can
Page 338:
Then add the PRIMARY KEY constraint
Page 342:
( ); FilmId integer NOT NULL, FilmN
Page 346:
ALTER TABLE Attendance ADD CONSTRAI
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
Page 396:
Chapter 5 Date Functions 178 Someti
Page 400:
Chapter 5 The syntax for the CAST()
Page 404:
Chapter 5 NULLs and Strings 182 NUL
Page 408:
Chapter 5 184 SELECT FirstName, Las
Page 412:
Chapter 5 186 This SQL copies over
Page 416:
Chapter 5 You also learned that mat
Page 420:
Chapter 6 190 Begin by looking at h
Page 424:
Chapter 6 This section covers queri
Page 428:
Chapter 6 194 This query gives the
Page 432:
Chapter 6 You’re almost there. Yo
Page 436:
Chapter 6 the database even though
Page 440:
Chapter 6 SELECT Category, AVG(DVDP
Page 444:
Chapter 6 Try It Out Selecting Data
Page 448:
Chapter 6 SELECT Category, COUNT(Fa
Page 454:
7 Selecting Data from Different Tab
Page 458:
Selecting Data from Different Table
Page 462:
Note that MS Access insists that yo
Page 466:
City State Orange Town New State Wi
Page 470:
SELECT FM1.FilmName FROM Films AS F
Page 474:
Selecting Data from Different Table
Page 478:
effects of any WHERE clause. There
Page 482:
Now re-execute the query. You get a
Page 486:
the category list and a list of whi
Page 490:
Category FirstName LastName Horror
Page 494:
You can join the results from two o
Page 498:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 502:
function and the query still works,
Page 506:
Summary Selecting Data from Differe
Page 512:
Chapter 8 A WHERE clause is added t
Page 516:
Chapter 8 238 FilmName PlotSummary
Page 520:
Chapter 8 If you think that your jo
Page 524:
Chapter 8 In the query, the Categor
Page 528:
Chapter 8 244 There is one area in
Page 532:
Chapter 8 246 SELECT FirstName, Las
Page 536:
Chapter 8 248 The subquery (SELECT
Page 540:
Chapter 8 250 Notice the use of the
Page 544:
Chapter 8 4. You should receive the
Page 548:
Chapter 8 254 This inner query retu
Page 552:
Chapter 8 It’s quite important no
Page 556:
Chapter 8 258 To tackle this query,
Page 560:
Chapter 8 260 Now you need to find
Page 566:
9 Advanced Queries In database prog
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
Page 598:
Executing the preceding query provi
Page 602:
GROUP BY SalesPerson.SalesPersonId,
Page 606:
Executing the preceding SQL creates
Page 610:
❑ Use IN with your subqueries. Wh
Page 614:
10 Views Views, as the name implies
Page 618:
Try It Out Building a View 1. The p
Page 622:
FROM dbo.MemberDetails INNER JOIN d
Page 626:
For example, you might want a list
Page 630:
However, if you take the case of Me
Page 634:
However, someone writes a query tha
Page 638:
Summary As you learned, views are l
Page 644:
Chapter 11 The information that fol
Page 648:
Chapter 11 This SQL adds formats (d
Page 652:
Chapter 11 TRANSACTION statement is
Page 656:
Chapter 11 Additionally, if a DBMS
Page 660:
Chapter 11 ROLLBACK TRANSACTION 310
Page 664:
Chapter 11 Transaction Logs 312 How
Page 668:
Chapter 11 Database There are perfe
Page 672:
Chapter 11 In order to find and fix
Page 676:
Chapter 11 When discussing locking,
Page 680:
Chapter 11 Usually, the default iso
Page 684:
Chapter 11 From Sue’s perspective
Page 688:
Chapter 11 5. At this point, you ne
Page 694:
12 SQL Security In today’s world,
Page 698:
Setting up security begins with cre
Page 702:
ALTER USER username options ALTER U
Page 706:
In Figure 12-3, three different gro
Page 710:
How It Works After you run this sta
Page 714:
check constraints can be used in a
Page 718:
You could then give SELECT privileg
Page 722:
Limitations on Views Views are by t
Page 726:
GRANT SELECT (NAME, SSN, SALARY) ON
Page 730:
Betsey also grants privileges to Ji
Page 734:
The CASCADE option tells the DBMS t
Page 738:
13 Database Tuning SQL is a languag
Page 742:
Perhaps this doesn’t sound remote
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
Page 792:
Appendix A 376 Figure A-1 ISBN is a
Page 796:
Appendix A Chapter 5 Exercise 1 Sol
Page 800:
Appendix A 380 You might receive sl
Page 804:
Appendix A 382 You should use the f
Page 808:
Appendix A Your answer may differ,
Page 812:
Appendix A WHERE (SELECT COUNT(*) f
Page 816:
Appendix A Exercise 2 Solution CREA
Page 820:
Appendix A Chapter 13 Exercise 1 So
Page 824:
Appendix B 392 Click the database i
Page 828:
Appendix B 394 Click Install to beg
Page 832:
Appendix B 396 Select the Detailed
Page 836:
Appendix B 398 Leave it at the defa
Page 840:
Appendix B 400 Having entered your
Page 844:
Appendix B 402 Figure B-20 The inst
Page 848:
Appendix B 404 At the very top of t
Page 852:
Appendix B 406 Having done that, ma
Page 856:
Appendix B 408 Figure B-30 MyTable
Page 860:
Appendix B 410 Figure B-32 Click Ne
Page 864:
Appendix B 412 Click Next to contin
Page 868:
Appendix B 414 Click OK to clear th
Page 872:
Appendix B If you’re ready and ha
Page 876:
Appendix B 418 You can also enter a
Page 880:
Appendix B 420 Figure B-49 The Film
Page 884:
Appendix B 422 Now you need to inse
Page 888:
Appendix B 424 In Access it’s not
Page 892:
Appendix B 426 Figure B-56 You need
Page 896:
Appendix B 428 Then click the Run i
Page 900:
Appendix B 430 The next screen (see
Page 904:
Appendix B 432 On the next screen,
Page 908:
Appendix B 434 Click Next to procee
Page 912:
Appendix B 436 Figure B-72 The huge
Page 916:
Appendix B 438 Figure B-74 Notice t
Page 920:
Appendix B 440 Figure B-76 The Obje
Page 924:
Appendix B 442 Figure B-78 Chapter
Page 928:
Appendix B You don’t need MyTable
Page 932:
Appendix B 446 Figure B-82 To begin
Page 936:
Appendix B Using Oracle’s SQL*Plu
Page 940:
Appendix B 450 Figure B-87 Another
Page 944:
Appendix C Category Table The follo
Page 948:
Appendix C 454 ( 3, ‘Sandra’,
Page 952:
Appendix C 456 ZipCode, Email, Date
Page 956:
Appendix C DateOfJoining ) VALUES (
Page 960:
Appendix C 460 VALUES ( 1, 3 ); INS
Page 964:
Appendix C VALUES ( 5, 3 ); INSERT
Page 968:
Appendix C 464 3 ); INSERT INTO Fil
Page 972:
Appendix C 5, 6 ); INSERT INTO Film
Page 976:
Appendix C 468 5 ); INSERT INTO Att
Page 980:
Appendix C Oracle 470 To save some
Page 984:
Appendix C 472 LocationId, MeetingD
Page 990:
Symbols + (addition operator), 82,
Page 994:
BEGIN TRANSACTION statement, 306, 3
Page 998:
SERIALIZABLE statement, 318 SET TRA
Page 1002:
data types brackets, 25 categories,
Page 1006:
Oracle concatenation, 85-88 configu
Page 1010:
error messages debugging, 26 subque
Page 1014:
concatenation, 85-88 data type comp
Page 1018:
primary keys database creation exam
Page 1022:
concurrent connection selection, 39
Page 1026:
passwords group access, 333 IBM ins
Page 1030:
ROLLBACK statement, 307-308 ROLLBAC
Page 1034:
REPEATABLE READ, 319 REVOKE, 344-34
Page 1038:
telephone numbers, data type select
Page 1042:
historical, data selection, 90-94 N
show all

Beginning SQL

Create successful ePaper yourself

Delete template?

Save as template?