1. Introduction to Relational Databases
Department of Computer and Information Science, School of Science, IUPUI Fall 2003
Introduction to Relational Databases
Dale Roberts, Lecturer
Computer Science, IUPUI
11/23/2018

2. Sharing Knowledge and Success
Oracle is a relational database management system (RDBMS).
RDBMSs allow users to...
put data in
keep/manage the data
get data out and work with it

3. Sharing Knowledge and Success
The Language of Oracle: SQL
Structured Query Language, English like query language
keywords: select, from, where, and order by
Example query: select city, temperature from weather where temperature > 80 order by temperature;
Examples of relational databases
stock tables in newspaper
sports scores
100 year example in book

4. Database Management
Disadvantages of traditional file processing systems…
uncontrolled redundancy
inconsistent data
inflexibility
limited data sharing
poor enforcement of standards
low programmer productivity
excessive program maintencance from Database Management, McFadden and Hoffer, pp. 8-14

5. Database Management: Data Models
Hierarchical Data Model (IMS)
nested sets of 1:1 or 1:M relationships
Network Data Model (IDMS, TOTAL)
multiple sets of 1:1, 1:M, M:1, or M:N relationships
Relational Data Model (Oracle, SQL Server, DB2)
relationships are NOT physically implemented
uses primary keys to represent associations
terminology: relations (tables), columns, tuples (rows), domain, degree, cardinality, primary keys, concatenated keys, alternate keys, foreign keys, Referential Integrity or R.I.
relational algebra, three main operators: select, project, join
normalization theory:1NF, 2NF, 3NF

6. Database Management: Normalization
First Normal Form (1NF)
Each column contains values about the same attribute, and each table cell value must be a single value.
Each column has a distince name, order of columns is immaterial.
Each row is distinct, rows cannot be duplicate for the same key
The sequence of rows is immaterial.
Second Normal Form (2NF)
All non-key attributes must be fully dependent on the whole key.
Third Normal Form (3NF)
Each nonkey attribute should be dependent only on the relation’s key, not on any other nonkey.

7. The Dangers in a Relational Database
It looks very easy to use a RDBMS
learning about normalization, SQL, etc. make for instant “experts.”
lack of experience with major production systems can create catastrophic project failures.
Testing cycles are getting shorter
newer development tools make software development quicker, usually systems testing gets shortened.
Recent college grads...
least experienced developers usually have more training with relational database technology.
veteran developers are busy with older projects.

8. The Dangers in a Relational Database
How to reduce the confusion…
Normalization 1NF: 2NF: 3NF: English names for tables and columns, English code names

9. The Dangers in a Relational Database

10. The Dangers in a Relational Database
Bad Examples of Table and Column Names:
Tables DEPT EMP EMPS MYEMPS PE PROJ TITLES PERSONNEL
Columns AD1 AU_LNAME AU_ORD BLOC CDLEXP DEPTNO DNAME DISCOUNTTYPE EMPNO ENAME ENUMBER ESAL HIGHQTY HIRANGE LORANGE LOWQTY NOTE ORD_NUM PNAME PROJNO PUBDATE QTYOH SLSTAXPCT WORKHRS
Reasons
abbreviation used without good reason
inconsistent abbreviations, underlines, and use of plurals
purpose not apparent from name
name rules have limitations

11. Chapter 2: The Dangers in a Relational Database
Use English Name for Data:
Poor Example: Better Example:

12. The Basic Parts of Speech in SQL
SQL is a language. Oracle7 SQL is a superset of the American National Standards Institute (ANSI) and the International Standards Organization (ISO) SQL92 standard at entry level conformance.
PL/SQL is Oracle’s procedural language extension to SQL. It allows you to link several SQL commands through procedural language.
SQL*Plus (SQLPLUS from command line) is a tool that allows users to interact with Oracle. SQL*Plus enables you to manipulate SQL commands and PL/SQL blocks, and to perform many additional tasks as well. Through SQL*Plus, you can:
enter, edit, store, retrieve, and run SQL commands and PL/SQL blocks
format, perform calculations on, store, and print query results in the form of reports
list column definitions for any table
access and copy data between SQL databases
send messages to and accept responses from an end user

13. The Basic Parts of Speech in SQL
SQL*Plus,… very quick overview
first, create/run a script to start an Oracle database instance
from the command line: sqlplus SQL>
Common commands in SQL*Plus:
get <filename>
@<filename>
save <filename>
list or l
change or c
edit
save
! (shell to OS)
Capitalization generally doen’t matter

14. Relational Algebra: The Basic Parts of Speech in SQL
manipulates 1 or 2 relations (tables) and returns 1 new relation as a result.
basic relational algebra operators are SELECT, PROJECT and JOIN.
SELECT returns a horizontal subset of a relation.
PROJECT returns a vertical subset of a relation
JOIN returns the combination of 2 relations based on common attributes. from Database Management, McFadden and Hoffer, pp

15. Select, Project, Select and Project
The Basic Parts of Speech in SQL
Select, Project, Select and Project
Join

16. Simple Select Examples
The Basic Parts of Speech in SQL
Simple Select Examples
Select statement, single table query, all rows:
SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE
FROM CUSTOMER
ORDER BY CUSTOMER_NUMBER;
... specific rows (where clause):
WHERE CUSTOMER_NUMBER > 500;
... with a calculation:
SELECT CUSTOMER_NUMBER, LAST, (CREDIT_LIM - BALANCE)
... multiple where conditions (and):
WHERE BALANCE >= 500
AND BALANCE <= 1000;

17. The Basic Parts of Speech in SQL
The SELECT clause:
can be a list of columns,
an asterik * for all columns,
a calculation (or other expressions),
group functions (chapter 9),
distinct keyword -- removes duplicates.
SELECT DISTINCT SUPPLIER
FROM PRODUCTS;
column names can be renamed in the output with an alias. SELECT CUSTOMER_NUMBER, LAST, FIRST, (CREDIT_LIM - BALANCE) AS REMAINING_CREDIT
FROM CUSTOMER;
The FROM clause:
in single tables queries, just provide your table’s name …. more on this in multi-table queries.

18. Chapter 3: The Basic Parts of Speech in SQL
The WHERE Clause:
this is a logical, boolean expression which must evalute to true for each row in the query’s output.
where clause comparison operators:
= equal to
<, > less than, greater than
<=, >= less than or equal, greater than or equal
<>, != , ^= not equal
compound conditions are built with the boolean operators AND, OR.
AND is evaluated first by default. Use parenthesis ( ) to force the order of OR/AND.
a compliment of a condition can be evaluated with NOT. Examples below are equivalent:
SELECT PART_DESCRIPTION FROM PART WHERE WAREHOUSE_NUMBER != ‘3’;
SELECT PART_DESCRIPTION FROM PART WHERE NOT (WAREHOUSE_NUMBER=‘3’);

19. The Basic Parts of Speech in SQL
The WHERE Clause (continued):
BETWEEN keyword is the same as >= and =<. For example, these 2 statements are the same: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE
FROM CUSTOMER
WHERE BALANCE >= 500 AND BALANCE <= 1000;
SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE
WHERE BALANCE BETWEEN 500 AND 1000;
LIKE keyword is used for pattern matching. ‘%’ is for any number of characters. ‘_’ (underscore) is for one character.
SELECT CUSTOMER_NUMBER, LAST, FIRST
FROM CUSTOMER WHERE LAST LIKE ‘JONE%’;
FROM CUSTOMER WHERE LAST LIKE ‘JONE_’;

20. The Basic Parts of Speech in SQL
The WHERE Clause (continued):
IN keyword provides a list of numbers or strings to compare to. This is similar to using OR with =. For example, these 2 statements are the same: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE
FROM CUSTOMER
WHERE CUSTOMER_NUMBER IN (10, 11, 12);
SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE
WHERE (CUSTOMER_NUMBER = 10)
OR (CUSTOMER_NUMBER = 11)
OR (CUSTOMER_NUMBER = 12);
NULL and NOT NULL keywords: NULL does not mean 0, null means no value! Example- this statement only gets customers whom we have a complete name for: SELECT CUSTOMER_NUMBER, LAST, FIRST FROM CUSTOMER WHERE (FIRST IS NOT NULL) AND (LAST IS NOT NULL);

21. The Basic Parts of Speech in SQL
The WHERE Clause (continued):
Values can also be compared to another query in the where clause. This is called a subquery. For example: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE
FROM CUSTOMER
WHERE CUSTOMER_NUMBER IN (SELECT CUSTOMER_NUMBER FROM CUSTOMER WHERE BALANCE > 500);
This however may not work sometimes with a subquery: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE
WHERE CUSTOMER_NUMBER = (SELECT CUSTOMER_NUMBER FROM CUSTOMER WHERE BALANCE > 500); because subqueries return sets of values, not a single value.

22. The Basic Parts of Speech in SQL
The WHERE Clause (continued):
Tables can be joined by common attributes. This is done in the where clause. SELECT WEATHER.CITY, CONDITION, TEMPERATURE, LATITUDE, FROM WEATHER, LOCATION WHERE WEATHER.CITY = LOCATION.CITY;
A shortcut (not in book). Tablenames can be aliased to save typing, reduce wordiness. SELECT W.CITY, CONDITION, TEMPERATURE, LATITUDE, FROM WEATHER W, LOCATION L WHERE W.CITY = L.CITY;
Joining data from different tables is one of the more powerful parts of SQL. It is not without its dangers.
Joining tables the wrong way (not on common attributes), the wrong data comes back.
Forgetting to specify common keys in the where clause returns a “cartesian product” (each row of both tables joined to each other, m times n rows)

23. The Basic Parts of Speech in SQL
The ORDER BY Clause:
Specifies the ordering of the returned data.
Multiple columns can be selected to sort on.
ASC is ascending order order, default.
DESC is descending sort order. SELECT FEATURE, SECTION, PAGE
FROM NEWSPAPER
WHERE SECTION = ‘F’ ORDER BY PAGE DESC, FEATURE ASC;
Views:
Makes a query act similar to a table.
Views are “describe”-able, “select”-able
The view’s select statement is ran everytime rows are selected from the view--ie data is not saved somewhere (like a table)
CREATE VIEW INVASION AS
SELECT W.CITY, CONDITION, TEMPERATURE, LATITUDE FROM WEATHER W, LOCATION L WHERE W.CITY = L.CITY;

24. Acknowledgements
These slides were originally prepared by Tony Teal as part of the IUPUI’s N311 Advanced Database Programming course.
11/23/2018