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Data Access Programming

Relational Database Management System (RDBMS)


• software system used to manage a relational database; typical
modern-day RDBMSs provide features for, among others:
o database creation
o querying and manipulation of data
o user accounts management
o data backup, restore, import, export facilities
o report generation
o database application development
o storage management
o performance tuning
• e.g., MS Access, MySQL, Oracle, MS SQL Server, Java DB, DB2, etc.

Database
• collection of data used by an application
• data is logically organized into tables (relations), which consists of
data rows and columns
o data row (a.k.a. record or tuple)
o data columns (a.k.a., fields or attributes)
• access to (and uniqueness of) data rows are facilitated through
primary keys
• associations among related tables are facilitated through foreign keys

Database Schema
• notation used to describe the structure of a database
• e.g.:
COURSES(course, description, years)
STUDENTS(idno, stname, course, yr)
FK course REF COURSES
SUBJECTS(codeno, description, units, schedule, fee)
ENROLL(idno, codeno)
FK idno REF STUDENTS
codeno REF SUBJECTS

Structured Query Language (SQL)


• language used to manipulate the data in a relational database
• used to create SQL queries, typically for data retrieval or manipulation
• SELECT Queries
o SELECT * FROM students;
o SELECT idno, stname FROM students;
o SELECT idno, stname FROM students WHERE course = ”BSIT”;
o SELECT idno, stname FROM students
WHERE course = ”BSMATH” AND (yr = 2 OR yr = 3);
o SELECT stname FROM students ORDER BY stname;
o SELECT stname FROM students ORDER BY stname DESC;
o SELECT UCase(stname) FROM students;
o SELECT description, fee * 0.25 AS discount FROM subjects;
o SELECT stname, courses.course, description
FROM courses, students
WHERE courses.course = students.course
ORDER BY course ASC, stname DESC;
o SELECT students.idno, stname, Sum(fee) AS totalfee
FROM students, enroll, subjects
WHERE students.idno = enroll.idno
AND enroll.codeno = subjects.codeno
GROUP BY students.idno, stname
ORDER BY stname;
• Data Manipulation Language (DML) Statements
o INSERT INTO students VALUES(1234, ”Erap”, ”BSIT”, 2);
o INSERT INTO secondyears
SELECT * FROM students WHERE yr = 2;
o UPDATE students SET yr = yr + 1 WHERE yr < 4;
o UPDATE students SET course = ”BSIM”, yr = 1
WHERE idno = 1234;
o DELETE * FROM students;
o DELETE * FROM students WHERE idno = 1234;

• Data Definition Language (DDL) Statements


o CREATE, DROP, RENAME, etc.
• Transaction Control Statements
o COMMIT, ROLLBACK, etc.