Relational Databases: Concepts, Keys, Integrity, and Joins (SQL Basics)

Notes

cs210– Relational Databases and SQL Basics Spring 2026 Prof. Amélie Marian Computer Science Rutgers University Relational Database: Definitions • Relational database: a set of relations • Relation: made up of 2 parts: • Instance : a table, with rows and columns. • Schema : specifies name of relation, plus name and type of each column. • E.G. Students(sid: string, name: string, login: string, age: integer, gpa: real). • Can think of a relation as a set of rows or tuples (i.e., all rows are distinct). Rutgers University This looks similar to a DataFrame but… • Relational databases avoid duplications and null values at all cost • This means that the data often needs to be separated (normalized) into several relations (tables). • There needs to be a way to connect information between tables Student ID Sname netid age GPA 53666 Jones j32 19 3.5 53688 Patel p993 18 3.0 53650 Patel p939 18 3.8 53831 Kim k565 19 2.1 Amélie Marian - CS210 - Rutgers University 3 Student ID 53666 53688 53650 53831 Sname Jones Patel Patel Kim Student Course Sem grade Course ID title Schedule 53666 cs111 F23 B cs111 Intro CS TTH5 53650 ece312 S24 A cs210 Data MW3 53666 ece312 F24 B ece312 Discrete MTH4 53831 cs...