1. Database Programming in Java

2. What are you going to learn about today?
MySQL database programming
Relational DB model
How to write SQL queries

3. Database (DB): Organized collection of data
Database Management System (DBMS): Controls the creation, maintenance, and use of a DB

4. Why use a DBMS?
Data independence: Applications need not be concerned with how data is stored or accessed
Provides a lot of functionality that would be silly to implement yourself:
Sharing (network)
Customizable security
Integrity

5. Two key aspects of a DBMS
Database model: How DB is structured and used
Examples: Relational, Object-Oriented, Hierarchical
Query language: Types of questions you can ask
Examples: SQL, XQuery
Relational + SQL is most common, so we’ll use MySQL

6. DB Tools DB client tools Code using DB library
Example: MySQL Workbench
Code using DB library
Lib example: Java Database Connectivity (JDBC)

7. Relational Model Concepts

8. Example Tables Authors AuthorISBN Publishers Titles AuthorID FirstName
LastName
YearBorn 1
Ayn
Rand
1905 2
Peter
Benchley
1940
AuthorISBN
Publishers
PublisherID
PublisherName 1
Bobbs Merrill 2
Random House
ISBN
AuthorID 1 2
Titles
ISBN
Title
EditionNumber
YearPublished
Description
PublisherID
The Fountainhead 1
1943 …
Atlas Shrugged
1957 2
Jaws
1973

9. Primary versus Foreign Keys
Primary key: Uniquely identifies each record in table
Foreign key: Field in table A such that the field is a primary key in one other table B
Authors
AuthorID
FirstName
LastName
YearBorn 1
Ayn
Rand
1905 …
AuthorISBN
ISBN
AuthorID 1 …

10. CRUD-to-SQL Mapping CRUD Operation SQL Statement Create INSERT
Read (Retrieve)
SELECT
Update (Modify)
UPDATE
Delete (Destroy)
DELETE
For complete documentation, see:

11. Example SELECT Queries—Let’s try them!
SELECT * FROM Authors
SELECT AuthorID, LastName FROM Authors
SELECT * FROM Authors WHERE YearBorn > 1910
SELECT * FROM Authors WHERE LastName LIKE ‘r%’
SELECT * FROM Authors WHERE LastName LIKE ‘_e%’
SELECT * FROM Authors WHERE LastName REGEX ‘[a-r]*’
SELECT * FROM Authors WHERE LastName REGEX ‘[a-r]*’ ORDER BY LastName ASC
For complete documentation, see

12. Use JOIN to merge data from multiple tables
SELECT FirstName, LastName, ISBN FROM Authors INNER JOIN AuthorISBN ON Authors.AuthorID = AuthorISBN.AuthorID ORDER BY LastName, FirstName
SELECT Titles.Title, Authors.LastName, Publishers.PublisherName FROM (Publishers INNER JOIN Titles ON Publishers.PublisherID = Titles.PublisherID) INNER JOIN (Authors INNER JOIN AuthorISBN ON Authors.AuthorID = AuthorISBN.AuthorID) ON Titles.ISBN = AuthorISBN.ISBN
For complete documentation, see

13. Basic steps for performing query with JDBC
Load driver class (only needs to be done once)
Connect to DB
Create/initialize statement
Execute statement (returns ResultSet)
Process ResultSet
Close connection (closes statement and ResultsSet)
For more complete documentation, see:

14. Let’s take a tour of a web app that uses JDBC
Let’s take a tour of a web app that uses JDBC

15. What could go wrong with this code? (Hint: Recall last lecture)
Check
Use
// Add 1 to each player’s Score
Statement qst = con.createStatement();
rs = qst.executeQuery("SELECT * FROM Players");
while (rs.next()) {
int playerID = rs.getInt("PlayerID");
int score = rs.getInt("Score");
Statement ust = con.createStatement();
ust.executeUpdate("UPDATE Players SET PlayerID = '" +
(score+1) +
"' WHERE PlayerID = '" + playerID + "'"); }
Score could change
TOCTOU race condition!
To avoid races, see transactions and/or table locks:

16. Summary Relational DBs CRUD to SQL mapping JDBC programming
Summary
Relational DBs
CRUD to SQL mapping
JOIN operation
JDBC programming
Watch out for race conditions!