This document provides an introduction to SQL (Structured Query Language) for working with relational databases. It covers basic SQL commands for creating tables, inserting data, updating data, retrieving data through queries, and deleting data. Examples are provided to demonstrate how to perform operations like selecting specific columns, sorting results, joining tables, and modifying data in a sample database of companies and employees. The overall purpose is to teach the fundamental data manipulation capabilities of SQL.

1. Introduction to Computer Science
Databases and SQL
Lecture c
This material (Comp 4 Unit 5) was developed by Oregon Health & Science University, funded by the Department
of Health and Human Services, Office of the National Coordinator for Health Information Technology under
Award Number 90WT0001.
This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International
License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/4.0/.

2. Databases and SQL
Learning Objectives - 1
• Define and describe the purpose of
databases (Lecture a)
• Define a relational database (Lecture a)
• Describe data modeling and normalization
(Lecture b)
• Describe the structured query language
(SQL) (Lecture c)
2

3. Databases and SQL
Learning Objectives - 2
• Define the basic data operations for
relational databases and how to
implement them in SQL (Lecture c)
• Design a simple relational database and
create corresponding SQL commands
(Lecture c)
• Examine the structure of a health care
database component (Lecture d)
3

4. SQL
• Used to manage and access database
information
• ANSI, ISO, and IEC standard
– DBMS have custom extensions!
• Extensive language
– We will look at a few basic commands
4

5. Example
• Make a space for the tables by creating
the database
– create database <name>
sql> create database contacts
• To remove
– drop database <name>
sql> drop database contacts
5

6. Create the Tables
• Create table <name> (<column
information>);
• Column information consists of column
names and data types
• Tables also have extra information
• To remove:
– drop table <name>
6

7. SQL Basic Data Types
Data Type Description
integer or int Whole numbers
float Floating point number
date Date
time Time
char (length) Fixed number of characters
varchar (length) Variable number of characters
Table 1. Basic data types and their descriptions in SQL.
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8. Create Company Table
sql> create table company (id
integer auto_increment,
-> name varchar(50),
-> address varchar(50),
-> city varchar(50),
-> state char(2),
-> primary key(id));
8

9. Create Person Table
sql> create table person(id
integer auto_increment,
-> first_name varchar(50),
-> last_name varchar(50),
-> company_id integer,
-> primary key(id),
-> foreign key(company_id)
references company(id));
9

10. View Tables
10

11. View Table Columns
11

12. Same Basic Operations
• Add an entry
• Retrieve an entry
• Delete an entry
• Modify an entry
12

13. Add an Entry
• Insert into <table> (columns) values
(values);
• First add company entries:
sql> insert into company (name, address, city, state)
-> values ('Community Hospital, Inc.', '1312 Main',
'Portland', 'OR');
sql> insert into company (name, address, city, state)
-> values ('Oakland Providers LLC', '14 12th St.',
'Oakland', 'CA');
13

14. Add Persons
• Now add people and companies
associated with them:
sql> insert into person (first_name, last_name, company_id)
-> values (‘Sriveni’, ‘Sharma’, 1);
sql> insert into person (first_name, last_name, company_id)
-> values (‘Walter’, ‘Chen’, 2);
sql> insert into person (first_name, last_name, company_id)
-> values (‘Rachel’, ‘Cohen’', 2);
sql> insert into person (first_name, last_name, company_id)
-> values (‘Karthik’, ‘Subramanian’, 1);
sql> insert into person (first_name, last_name, company_id)
-> values (‘Kelly’, ‘David’, 2);
14

15. Retrieve an Entry
• Select <columns> from <table>;
• Get company information:
15

16. Add Sorting
• Get people, sorted by last name:
sql> select * from person order by last_name;
16

17. Add Selectivity
• Get names of people who work for
Community Hospital:
sql> select first_name, last_name from where company_id = 1;
17

18. Retrieve from Multiple Tables
• Select <columns> from <table 1> join
<table 2> on <table 1 foreign key> =
<table 2 primary key>;
sql> select * from person join company on person.company_id = companyid;
18

19. Create a Complex SQL Statement
sql> select first_name, last_name, company.name from
person join company on person.company_id =
company.id order by last_name;
19

20. Delete an Entry
• Delete from <table> where <constraints>;
• Remove Rachel from contact list:
sql> delete from person where
first_name=‘Rachel’ and
last_name=‘Cohen’;
1 row affected
20

21. Modify an Entry
• update <table> set <column>=<data>
where <constraints>;
21

22. New Company Name - 1
• Our example where “Community Hospital,
Inc.” becomes “Community General”
– Get the id
sql> select * from company;
– Update the row data
sql> update company set name ‘Community
General’ where id=1;
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23. New Company Name - 2
• Just for us, verify the change
sql> select * from company;
23

24. Verify Again
sql> select first_name, last_name, company.name from
person join company on person.company_id –
company.id order by last_name;
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25. Databases and SQL
Summary – Lecture c
• SQL is a language for creating, accessing
and updating databases
– Create tables
– Insert data
– Update data
– Retrieve (select) data
– Delete data
25

26. Databases and SQL
References – Lecture c
References
Chen, P. P. (1976). The Entity-Relationship Model - Toward a Unified View of Data. ACM
Transactions on Database Systems, 1(1).
International Organization for Standardization. (2008). Information technology –
Database languages – SQL (No. ISO/IEC 9075-(1-4,9-11,13,14)).
Kent, W. (1983). A simple guide to five normal forms in relational database theory.
Communications of the ACM, 26(2).
26

27. Introduction to Computer Science
Databases and SQL
Lecture c
This material was developed by Oregon
Health & Science University, funded by the
Department of Health and Human Services,
Office of the National Coordinator for Health
Information Technology under Award
Number 90WT0001.
27