 SQL(pronounced
“sequel”)-Structured Query
Language
 Syntax extensions were added by individual
vendors and made their way into…
 ANSI(American National Standards Institute)
SQL, the standard relational databases used
today.
 SQL is used by most commercial database
applications. No viable alt. language.
 Evolves, but basic functionality remains
unchanged.
A
database is an organized collection of data.
 A database management system (DBMS) is
software that allows the creation, retrieval,
and manipulation of data.
 A relational database management system
(RDBMS) provides this functionality within
the context of the relational database theory
and the rules defined by Codd.
 Data
is all around; you make use of it every
day. When registering for a class, interacting
with an ATM, etc..
 Data independence, a user does not need to
know on which hard drive and file a
particular piece of information is stored.
 This provides data consistency and data
integrity.
 A relational database stores data in tables,
essentially a two-dimensional matrix
consisting of columns and rows.
 Generally
contains data about a single
subject
 Each table has a unique name that signifies
the contents of the data
 A database consists of many tables.
 Columns
in a table organize the data further.
 A table consists of at least one column.
 Each column represents a single, low-level
detail about a set of data
 The name of each column is unique within a
table and identifies the data you find in that
column
 Each
row usually represents one unique set
of data within a table.
 All of the columns of the rows represent
respective data for the row.
 Each intersection of a column and row in a
table represents a value.
BOOK_ID
TITLE
PUBLISHER
1010
The Invisible
Force
Literacy Circle
1011
Into The Sky
Prentice Hall
Column
PUBLISH_DATE
ROW
10/2008
 No
value is said to be NULL.
 Blanks are not nulls.
 Nulls cannot be compared or evaluated
because they are unknowns.
 null is not greater or less than null
 null ≠null
 Need
to uniquely identify data within a
table.
 You find there is one and only one row in the
table by looking for the primary key value.
 A system-generated sequence number is
called a synthetic or surrogate key.
 Best to avoid any primary key that is subject
to change.
 Only one primary key per table.
 More than one column in the primary key is
called a composite or concatenated primary
key
 Rather
than store rows with repetitive data,
the table can be normalized to remove
duplications.
 A foreign key is where primary key column(s)
in a table links to a column(s) in another
table which provides more detail information
for the original table.
 Within
the SQL language there are individual
sublanguages
 Data Manipulation Language(DML) commands
allow you to query, insert, update, and
delete data.
 Data Definition Language(DDL) allows you to
create new database structures such as
tables and modify existing ones.
 Data Control Language(DCL) allows you to
control access to the data.
 Go
to page 8 in book
 Answer and discuss answers in class.
 Eliminates
redundancy in tables, avoiding
future data manipulation problems.
 There are several different rules for
minimizing duplication of data, called normal
forms.
 There are many different normalization rules
but the five normal forms and the BoyceCodd normal form(BCNF) are the most
accepted.
 All
repeating groups must be removed and
placed in a new table.
 This design provides more flexibility with the
data and less overhead.
 Minimizes the need to create multiple rows
for one unique identifier.
1NF
 Uses
the First Normal Form rules and…
 All the nonkey columns must depend on the
entire primary key.
 Applies only to composite primary keys.
 Uses
the Second Normal Form rules and…
 Every nonkey column must be a fact about
the primary key.
 If an attribute depends on a nonkey column
then that attribute needs to be moved a
different table.
2NF & 3NF
Book-Author table
shows the violation of
the second normal form
This table shows
the violation of
the third normal
form
The Book & the
Publisher tables in
the 3rd normal form
 BCNF
is an elaborate version of third normal
form and deals with deletion anomalies.
 Fourth Normal Form tackles potential
problems when three or more columns are
part of the unique identifier and their
dependencies to each other.
 Fifth Normal Form splits the tables even
further apart to eliminate all redundancy.
When two tables have common column(s), they
are said to have a relationship. The cardinality
of a relationship is the actual number of
occurrences between them.
 (1:M) One-to-many relationship: The most
common relationship. The shared column(s) of
one table links to many rows in the other.
 (1:1) One-to-one relationship: The shared
column(s) are unique in each table.
 (M:M) Many-to-many relationship: The shared
column(s) of each table have multiple rows for
each unique value.
 Following the rules of relational database, an
associative table or intersection table resolves
the M:M problem.

 Database
schema diagrams are used to
graphically depict the relationship between
tables.
 A “crow’s foot” on one end represents the
1:M relationship.
BOOK_ID
PUBLISHER_ID
TITLE
PUBLISHER_NAME
PUBLISHER_ID(FK)
PHONE_NO
 The
cardinality expresses the ratio of a
parent and child table from the perspective
of the parent table. It describes how many
rows you may find between the two tables
for a given primary key value.
 The optionality of a relationship is whether
or not a row is required (mandatory or
optional). It shows whether one row in a
table can exist without a row in the related
table.
 In
an identifying relationship, the primary
key is propagated to the child entity as part
of the primary key.
 In a nonidentifying relationship, the foreign
key becomes one of the nonkey columns.
Nulls are accepted in the foreign key column.
 Round edges on a diagram mean the
relationship is identifying. Sharp edges mean
nonidentifying.
 Requirements
Analysis—Gather data
requirements that identify the needs and
wants of the users. One of the outputs of his
phase is a list of individual data elements
that need to be stored.
 Conceptual Data Model—Groups the major
data elements from the requirements
analysis into individual entities with each
individual data element referred to as an
attribute. Unique identifiers or candidate
keys that uniquely distinguish each row are
determined. Noncritical attributes are not
included in the model.


Logical Data Model—Shows that all the entities, their
respective attributes, and the relationship between
entities represent the business requirements, without
considering the technical issues. Descriptive names
and documentation is required. The complete model
is called the logical data model, or entity relationship
diagram (ERD). In the end, entities are fully
normalized, the unique identifier for reach entity is
determined, and any many-to-many relationships are
resolved into associative entities.
Physical Data Model—Also referred to as the database
schema diagram is a graphical model of the physical
design implementation of the database. There may
be many physical models to choose from. This model
uses different terminology. Tables instead of entities,
columns instead of attributes, etc..
 Entities
are resolved to physical tables.
 Attributes become columns with specific
data types and formats.
 Data integrity and consistency are created
and physical storage parameters for
individual tables are determined.
 Indexes are designed. They are database
objects that facilitate speedy access to data
with the help of a specific column(s) of a
table. Indices enhance query performance
but they also create overhead when
performing deletes/inserts/updates.





The act of adding redundancy to the physical
database design.
Data designers or architects sometimes purposely add
redundancy to their design to increased query
performance.
In some application where massive amounts of
detailed data are stored and summarized,
denormalization is required.
Data warehouse applications are database
applications that benefit users who need to analyze
large data sets from various angles and use this data
for reporting and decision-making purposes.
The primary purpose of a data warehouse is to query,
report, and analyze data. Therefore, redundancy is
encouraged and necessary for queries to perform
efficiently.
 Go
to page 27 in book
 Answer and discuss answers in class.
 Throughout
this book and the course the
database for a school’s computer education
program is sued as a case study on which
most exercises are based.
 It is important to familiarize yourself with
the STUDENT case study diagram.
 The STUDENT table contains data about each
individual student, such as his or her name,
address, employer, and the date the student
registered in the program.
 Data
Types are found next to each column
name in the diagram. Each column can
contain a different type of data. Some of
the possible data types are as follows:
Data Type
Data Description
VARCHAR2(n)
A variable length of alphanumeric
characters with a max of n characters
CHAR(n)
A fixed-length of alphanumeric
characters having n characters. Any
unused space is padded with blanks
until n is reached.
NUMBER(x,y)
A numeric value with a max length of
x digits and y decimal places
DATE
Stores both date and time
The COURSE table lists all the available courses
that a student may take. The table consists of a
PREREQUISITE, a COURSE_NO, a DESCRIPTION,
and a COST column. COURSE_NO is the key.
 The COURSE table represents a recursive or selfreferencing relationship.
 A recursive relationship means a column within a
table references another column within the
same table.
 In the COURSE table, the PREREQUISITE column
shows which course_no is needed to be
completed before the current course_no can be
taken.
 Nulls are allowed here because the relationship
is optional.

The SECTION table includes all the individual
sections a course may have. An individual course
may have zero, one, or many sections, each of
which can be taught in different rooms, at
different times, and by different instructors.
SECTION_ID is the primary key of the table.
COURSE_NO is a foreign key. STATE_DATE_TIME
shows the date and time the section meets,
LOCATION lists the classroom, and CAPACITY
shows the maximum number of students that
may enroll.
 A natural key is a set of column(s) that naturally
uniquely identify a row. A computer generated
sequence number, called a surrogate key, can be
used as a substitute of the natural key..

The INSTRUCTOR_ID column is another foreign
key column in the SECTION table, linking to the
INSTRUCTOR table.
 An INSTRUCTOR must always be assigned to a
SECTION. It can never be null. But an
INSTRUCTOR doesn’t have to teach a class.
 A COURSE may have zero, one, or multiple
sections.
 The INSTRUCTOR table lists information related
to an individual instructor, such as name,
address, phone, and zip code. The primary key
is INSTRUCTOR_ID. The ZIP column is the foreign
key column to the ZIPCODE table.

 Referential
integrity does not allow deletion
of a primary key value in a parent table that
exists in a child as a foreign key table. This
would create orphan rows in the child table.
 The ENROLLMENT table is an intersection
table between the STUDENT and the SECTION
table, listing the students enrolled in the
various section. It has a composite primary
key of STUDENT_ID and SECTION_ID.
ENROLL_DATE contains the date the student
registered and FINAL_GRADE lists the
student’s final grade. A STUDENT may be
enrolled in zero, one, or many sections.
The GRADE_TYPE table is a lookup table for
other tables as it relate to grade information.
GRADE_TYPE_CODE in the primary key and lists
the unique category of grade. DESCRIPTION
describes the abbreviated code.
 The GRADE table lists all the grades related to
the section in which a student is enrolled.
GRADE_CODE_OCCURENCE is a sequence number
listing the order of the grade, while
NUMERIC_GRADE lists actual grade value.
GRADE_CONVERSION in the numeric grade
converted to a letter. The primary key columns
are STUDENT_ID, SECTION_ID,
GRADE_TYPE_CODE, and
GRADE_CODE_OCCURENCE.

 The
GRADE_TYPE_WEIGHT table aids in
computation of the final grade a student
receives for an individual section. Different
sections can have finals computed
differently. The final grade is determined by
using the individual grades of the student
and section in the GRADE table in
conjunction with this table. The primary key
consists of the SECTION_ID and
GRADE_TYPE_CODE columns. A
GRADE_TYPE_CODE can exist zero, one, or
many times.
 Go
to page 41 in book
 Answer and discuss answers in class.
 Quiz
will be given at the beginning of our
next class