SQL VISUAL QUICKSTART GUIDE- P8 pdf

books contains five tables that contain infor-mation about authors, titles they’ve pub-lished, their publishers, and their royal-ties.. Table 2.3 shows the structure of the table aut

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Other normal forms

Higher levels of normalization exist, but the

relational model doesn’t require (or even

mention) them They’re useful in some cases

to avoid redundancy Briefly, they are:

rigor-ous version of 3NF BCNF deals with

tables that have multiple candidate keys,

composite candidate keys, or candidate

keys that overlap A table is in BCNF if

every determinant is a candidate key

(A determinant column is one on which

some of the columns are fully functionally

dependent.)

◆ A table in fourth normal form is in BCNF

and has no multivalued dependencies

(MVDs) An MVD occurs when in a table

containing at least three columns, one

column has multiple rows whose values

match a value of a single row of one of

the other columns.

Suppose that employees can be assigned

to multiple projects and each employee

can have multiple skills If you stuff all

this information into a single table, you must use all three attributes as the key because nothing less can identify a row uniquely The relationship between emp_id and proj_id is an MVD because for each pair of emp_id / skill_id values

in the table, only emp_id (independent

of skill_id ) determines the associated set of proj_id values The relationship between emp_id and skill_id also is an MVD because the set of skill values for

an emp_id / proj_id pair always depends

on only emp_id To transform a table with MVDs to 4NF, move each MVD pair to a new table.

◆ A table in fifth normal form is in 4NF and

has no join dependencies, which are gen-eralizations of MVDs The aim of 5NF is

to have tables that can’t be decomposed further into any number of smaller tables The redundancies and anomalies that 5NF cures are rare and unintuitive In real databases, you’ll see 1NF, 2NF, 3NF, and occasionally 4NF 4NF and even 3NF tables almost always are 5NF too.

Denormalization

The increased number of tables that normalization generates might sway you to denormalize

your database to speed queries (because having fewer tables reduces computationally expen-sive joins and disk I/O) This common technique trades off data integrity for performance and presents a few other problems A denormalized database:

◆ Usually is harder to understand than a normalized one

◆ Usually makes retrievals faster but updates slower

◆ Increases the risk of inserting inconsistent data

◆ Might improve the performance of some database applications but hurt that of others (because users’ table-access patterns change over time)

The need for denormalization isn’t a weakness in the relational model but reveals a flawed implementation of the model in DBMSs A common use for denormalized tables is as perma-nent logs of data copied from other tables The logged rows are redundant, but because they’re only INSERT ed (never UPDATE d), they serve as an audit trail immune to future changes

in the source tables.

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The Sample Database

Pick up an SQL or database-design book, and

probably you’ll find a students/courses/

teachers, customers/orders/products, or

authors/books/publishers database In a bow

to convention, most of the SQL examples in

this book use an authors/books/publishers

sample database named books Here are some

things that you should know about books :

◆ Recall from “Tables, Columns, and Rows”

earlier in this chapter that a database

appears to the user as a collection of

tables (and nothing but tables) books

contains five tables that contain

infor-mation about authors, titles they’ve

pub-lished, their publishers, and their

royal-ties Figure 2.21 depicts the tables and

relationships in books by using the

graphical conventions introduced earlier

in this chapter.

◆ The SQL statements in Chapters 10 and later modify data in books (rather than just retrieve data) Unless I note otherwise, each new section in a chapter starts with a pristine copy of books In other words, assume that database changes made in one section don’t carry over to the next section.

◆ Some of the concepts mentioned in this section, such as data types and nulls, are covered in the next chapter.

◆ books is a teaching tool; its structure and size don’t approach the complexity of real production databases.

◆ To create the sample database on your own DMBS, see “Creating the Sample Database” later in this chapter.

authors au_id

au_fname

au_lname

phone

address

city

state

zip

title_authors title_id au_id au_order royalty_share

publishers pub_id pub_name city state country

titles title_id title_name type pub_id pages price sales pubdate contract

royalties title_id advance royalty_rate

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The table authors

The table authors describes the books’

authors Each author has a unique identifier

that’s the primary key Table 2.3 shows

the structure of the table authors , and

Figure 2.22 shows its contents.

Table 2.3

authors Table Structure

C o l u m n N a m e D e s c r i p t i o n D a t a T y p e N u l l s ? K e y s

au_id Unique author identifier CHAR(3) PK

au_fname Author first name VARCHAR(15)

au_lname Author last name VARCHAR(15)

phone Author telephone number VARCHAR(12) Yes

address Author address VARCHAR(20) Yes

city Author city VARCHAR(15) Yes

state Author state CHAR(2) Yes

zip Author zip (postal) code CHAR(5) Yes

au_id au_fname au_lname phone address city state zip - -A01 Sarah Buchman 718-496-7223 75 West 205 St Bronx NY 10468 A02 Wendy Heydemark 303-986-7020 2922 Baseline Rd Boulder CO 80303 A03 Hallie Hull 415-549-4278 3800 Waldo Ave, #14F San Francisco CA 94123 A04 Klee Hull 415-549-4278 3800 Waldo Ave, #14F San Francisco CA 94123 A05 Christian Kells 212-771-4680 114 Horatio St New York NY 10014 A06 Kellsey 650-836-7128 390 Serra Mall Palo Alto CA 94305 A07 Paddy O'Furniture 941-925-0752 1442 Main St Sarasota FL 34236

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The table publishers

The table publishers describes the books’

publishers Every publisher has a unique

identifier that’s the primary key Table 2.4

shows the structure of the table publishers ,

and Figure 2.23 shows its contents.

Table 2.4

publishers Table Structure

C o l u m n N a m e D e s c r i p t i o n D a t a T y p e N u l l s K e y s

pub_id Unique publisher identifier CHAR(3) PK

pub_name Publisher name VARCHAR(20)

city Publisher city VARCHAR(15)

state Publisher state/province CHAR(2) Yes

country Publisher country VARCHAR(15)

pub_id pub_name city state country

- - - -

-P01 Abatis Publishers New York NY USA

P02 Core Dump Books San Francisco CA USA

P03 Schadenfreude Press Hamburg NULL Germany

P04 Tenterhooks Press Berkeley CA USA

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The table titles

The table titles describes the books Every

book has a unique identifier that’s the

pri-mary key titles contains a foreign key,

pub_id , that references the table publishers

to indicate a book’s publisher Table 2.5

shows the structure of the table titles ,

and Figure 2.24 shows its contents.

Table 2.5

titles Table Structure

title_id Unique title identifier CHAR(3) PK

title_name Book title VARCHAR(40)

type Subject of the book VARCHAR(10) Yes

pub_id Publisher identifier CHAR(3) FK publishers(pub_id) pages Page count INTEGER Yes

price Cover price DECIMAL(5,2) Yes

pubdate Date of publication DATE Yes

contract Nonzero if author(s) signed SMALLINT

contract

Lifetime number of copies sold

title_id title_name type pub_id pages price sales pubdate contract - - - - -T01 1977! history P01 107 21.99 566 2000-08-01 1 T02 200 Years of German Humor history P03 14 19.95 9566 1998-04-01 1 T03 Ask Your System Administrator computer P02 1226 39.95 25667 2000-09-01 1 T04 But I Did It Unconsciously psychology P04 510 12.99 13001 1999-05-31 1 T05 Exchange of Platitudes psychology P04 201 6.95 201440 2001-01-01 1 T06 How About Never? biography P01 473 19.95 11320 2000-07-31 1 T07 I Blame My Mother biography P03 333 23.95 1500200 1999-10-01 1 T08 Just Wait Until After School children P04 86 10.00 4095 2001-06-01 1 T09 Kiss My Boo-Boo children P04 22 13.95 5000 2002-05-31 1 T10 Not Without My Faberge Egg biography P01 NULL NULL NULL NULL 0 T11 Perhaps It's a Glandular Problem psychology P04 826 7.99 94123 2000-11-30 1 T12 Spontaneous, Not Annoying biography P01 507 12.99 100001 2000-08-31 1 T13 What Are The Civilian Applications? history P03 802 29.99 10467 1999-05-31 1

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The table title_authors

Authors and books have a many-to-many relationship, because an author can write multiple books and a book can have multiple authors title_authors is the junction table that associates the tables authors and titles ; see “Relationships” earlier in this chapter title_id and au_id together form

a composite primary key, and each column separately is a foreign key that references titles and authors , respectively The non-key columns indicate the order of the author’s name on the book’s cover (always 1 for a book with a sole author) and the fraction

of total royalties that each author receives (always 1.0 for a book with a sole author).

Table 2.6 shows the structure of the table

title_authors , and Figure 2.25 shows

its contents.

title_id au_id au_order royalty_share

- - -

-T01 A01 1 1.00

T02 A01 1 1.00

T03 A05 1 1.00

T04 A03 1 0.60

T04 A04 2 0.40

T05 A04 1 1.00

T06 A02 1 1.00

T07 A02 1 0.50

T07 A04 2 0.50

T08 A06 1 1.00

T09 A06 1 1.00

T10 A02 1 1.00

T11 A03 2 0.30

T11 A04 3 0.30

T11 A06 1 0.40

T12 A02 1 1.00

T13 A01 1 1.00

Table 2.6

title_authors Table Structure

title_id Title identifier CHAR(3) PK, FK titles(title_id) au_id Author identifier CHAR(3) PK, FK authors(au_id)

au_order Author name order on book cover SMALLINT

royalty_share Author fractional royalty share DECIMAL(5,2)

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The table royalties

The table royalties specifies the royalty

rate paid to all the authors (not each author)

of each book, including the total up-front

advance against royalties paid to all authors

(again, not each author) of a book The

royalties primary key is title_id The

table royalties has a one-to-one

relation-ship with titles , so the royalties primary

key also is a foreign key that references

the titles primary key Table 2.7 shows

the structure of the table royalties , and

Figure 2.26 shows its contents.

title_id advance royalty_rate - - -T01 10000.00 0.05 T02 1000.00 0.06 T03 15000.00 0.07 T04 20000.00 0.08 T05 100000.00 0.09 T06 20000.00 0.08 T07 1000000.00 0.11 T08 0.00 0.04 T09 0.00 0.05 T10 NULL NULL T11 100000.00 0.07 T12 50000.00 0.09 T13 20000.00 0.06

Table 2.7

royalties Table Structure

title_id Unique title identifier CHAR(3) PK, FK titles(title_id) advance Up-front payment to author(s) DECIMAL(9,2) Yes

royalty_rate Fraction of revenue paid author(s) DECIMAL(5,2) Yes

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Creating the Sample Database

To create (or re-create) the database books

on your own DMBS, visit www.fehily.com , click the Downloads link for this book, and then follow the onscreen instructions.

Creating books is a two-step process:

1. Use your DBMS’s built-in tools to create

a new, blank database named books

2. Run an SQL script that creates tables within books and populates them with data.

Listing 2.1 shows a standard (ANSI) SQL

script that creates the sample-database tables and inserts rows into them.

■ If you’re using Microsoft

Access, you don’t two-step—

you simply open an mdb file in Access.

populates them with data The file that you download at the companion website includes versions of this script

changed to run on specific DBMSs.

DROP TABLE authors;

CREATE TABLE authors

(

au_id CHAR(3) NOT NULL,

au_fname VARCHAR(15) NOT NULL,

au_lname VARCHAR(15) NOT NULL,

phone VARCHAR(12) ,

address VARCHAR(20) ,

city VARCHAR(15) ,

state CHAR(2) ,

zip CHAR(5) ,

CONSTRAINT pk_authors PRIMARY KEY (au_id)

);

INSERT INTO authors VALUES('A01','Sarah','Buchman','718-496-7223',

'75 West 205 St','Bronx','NY','10468');

INSERT INTO authors VALUES('A02','Wendy','Heydemark','303-986-7020',

'2922 Baseline Rd','Boulder','CO','80303');

INSERT INTO authors VALUES('A03','Hallie','Hull','415-549-4278',

'3800 Waldo Ave, #14F','San Francisco','CA','94123');

(listing continues on next page)

Listing

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Listing 2.1 continued

INSERT INTO authors VALUES('A04','Klee','Hull','415-549-4278',

'3800 Waldo Ave, #14F','San Francisco','CA','94123');

INSERT INTO authors VALUES('A05','Christian','Kells','212-771-4680',

'114 Horatio St','New York','NY','10014');

INSERT INTO authors VALUES('A06','','Kellsey','650-836-7128',

'390 Serra Mall','Palo Alto','CA','94305');

INSERT INTO authors VALUES('A07','Paddy','O''Furniture','941-925-0752',

'1442 Main St','Sarasota','FL','34236');

DROP TABLE publishers;

CREATE TABLE publishers

(

pub_id CHAR(3) NOT NULL,

pub_name VARCHAR(20) NOT NULL,

city VARCHAR(15) NOT NULL,

state CHAR(2) ,

country VARCHAR(15) NOT NULL,

CONSTRAINT pk_publishers PRIMARY KEY (pub_id)

);

INSERT INTO publishers VALUES('P01','Abatis Publishers','New York','NY','USA');

INSERT INTO publishers VALUES('P02','Core Dump Books','San Francisco','CA','USA');

INSERT INTO publishers VALUES('P03','Schadenfreude Press','Hamburg',NULL,'Germany');

INSERT INTO publishers VALUES('P04','Tenterhooks Press','Berkeley','CA','USA');

DROP TABLE titles;

CREATE TABLE titles

(

title_id CHAR(3) NOT NULL,

title_name VARCHAR(40) NOT NULL,

type VARCHAR(10) ,

pub_id CHAR(3) NOT NULL,

pages INTEGER ,

price DECIMAL(5,2) ,

sales INTEGER ,

pubdate DATE ,

contract SMALLINT NOT NULL,

CONSTRAINT pk_titles PRIMARY KEY (title_id)

);

INSERT INTO titles VALUES('T01','1977!','history','P01',

107,21.99,566,DATE '2000-08-01',1);

INSERT INTO titles VALUES('T02','200 Years of German Humor','history','P03',

14,19.95,9566,DATE '1998-04-01',1);

INSERT INTO titles VALUES('T03','Ask Your System Administrator','computer','P02',

1226,39.95,25667,DATE '2000-09-01',1);

INSERT INTO titles VALUES('T04','But I Did It Unconsciously','psychology','P04',

510,12.99,13001,DATE '1999-05-31',1);

INSERT INTO titles VALUES('T05','Exchange of Platitudes','psychology','P04',

201,6.95,201440,DATE '2001-01-01',1);

INSERT INTO titles VALUES('T06','How About Never?','biography','P01',

473,19.95,11320,DATE '2000-07-31',1);

Listing

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Listing 2.1 continued

INSERT INTO titles VALUES('T07','I Blame My Mother','biography','P03',

333,23.95,1500200,DATE '1999-10-01',1);

INSERT INTO titles VALUES('T08','Just Wait Until After School','children','P04',

86,10.00,4095,DATE '2001-06-01',1);

INSERT INTO titles VALUES('T09','Kiss My Boo-Boo','children','P04',

22,13.95,5000,DATE '2002-05-31',1);

INSERT INTO titles VALUES('T10','Not Without My Faberge Egg','biography','P01',

NULL,NULL,NULL,NULL,0);

INSERT INTO titles VALUES('T11','Perhaps It''s a Glandular Problem','psychology','P04',

826,7.99,94123,DATE '2000-11-30',1);

INSERT INTO titles VALUES('T12','Spontaneous, Not Annoying','biography','P01',

507,12.99,100001,DATE '2000-08-31',1);

INSERT INTO titles VALUES('T13','What Are The Civilian Applications?','history','P03',

802,29.99,10467,DATE '1999-05-31',1);

DROP TABLE title_authors;

CREATE TABLE title_authors

(

au_id CHAR(3) NOT NULL,

au_order SMALLINT NOT NULL,

royalty_share DECIMAL(5,2) NOT NULL,

CONSTRAINT pk_title_authors PRIMARY KEY (title_id, au_id)

);

INSERT INTO title_authors VALUES('T01','A01',1,1.0);

DROP TABLE royalties;

CREATE TABLE royalties

(

advance DECIMAL(9,2) ,

royalty_rate DECIMAL(5,2) ,

CONSTRAINT pk_royalties PRIMARY KEY (title_id)

);

Listing

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