Module 7: Databases

1. A database is an organized collection of related data that many people and programs can use at the same time. A spreadsheet is fine for one person's list; a database is built for many users, large volumes, and questions asked over and over.
2. A table stores one kind of thing (students, courses, orders). Each row is a record — one student. Each column is a field — Last Name, Grade, Phone Number. Every field has a data type: text, number, date, currency, yes/no.
3. The primary key is the field that uniquely identifies each record — Student ID, not Last Name, because two students can share a name. No two records may have the same primary key, and it may not be blank.
4. A relational database stores data in several tables and connects them with keys. A foreign key in one table (Course ID in the Enrollment table) points to the primary key of another (Course ID in the Courses table). That link is the relationship.
5. Why split data into tables? To avoid repeating it. If every enrollment row also stored the student's full address, a change of address would have to be made in dozens of rows. Store the address once, in the Students table, and link by Student ID. This is normalization.
6. A database management system (DBMS) is the software that creates, stores, secures, and answers questions about the data: Microsoft Access, MySQL, Microsoft SQL Server, Oracle, PostgreSQL.
7. A query is a question you ask the database. SQL (Structured Query Language) is the standard language for asking it. SELECT * FROM students; returns every column of every student. SELECT last_name, grade FROM students WHERE grade = 9; returns only the 9th graders' names and grades.
8. SQL verbs to know: SELECT reads data, INSERT adds a record, UPDATE changes a record, DELETE removes one. WHERE filters rows; ORDER BY sorts them.
9. Forms are how people enter data into a database; reports are formatted output for people to read; queries sit in between. Access uses all three on top of its tables.
10. Data quality matters: a database is only as good as what goes in. Validation rules (a grade must be 9–12, a date must be a real date) stop bad data at the door.
11. Big data means data sets so large, fast, or varied that traditional tools struggle: web clicks, sensors, video, social posts. Data warehouses collect data from many systems for analysis; business intelligence and data mining find patterns in it.
12. Databases carry responsibility: personal data (grades, addresses, health) must be protected, and only people with a need should be able to read it. Prof. Roberts' Canvas gradebook is a database with exactly those rules.
13. Module 7 items: Database Assignment (50) and Module 7 Quiz (20) — 70 points, the week of Oct 12. Module 8 (The People in Information Systems) follows the week of Oct 19.

Raise your hand. Mr. James gets a message right away and can help you remotely. Nothing else is stored — just your last name, grade, and where you're stuck.

Ask at home: Where does a store keep track of what it sells? What would a table of that data look like?

En español: ¿Dónde lleva una tienda el registro de lo que vende? ¿Cómo sería una tabla con esos datos?