Relational database management systems (RDBMS, or more simply, relational databases) are systems that are used to store and retrieve data, and allow the data to be structured such that we can create relationships between the data. So we can do things like store data about students, store data about courses, and define relationships that connect students to the courses they are taking.
The basic structure of relational databases are tables, rows, columns. Think of a relational database as many spreadsheets, where each spreadsheet is a table, and consists of many rows and columns. Each table represents a thing that we want to store data about – maybe a student, a course, or a purchase. Each column in a table corresponds to a different piece of data that we’d like to collect about that thing. So columns in a student table could be: first name, last name, address, major, student number. Each row in a table corresponds to one record in that table. So for a student table, each row would be data for a different student, and include most or all of the data we defined in the columns for a student.
To interact with most relational databases, we use structured query language or SQL. With SQL, we can create/retrieve/update/delete (also sometimes referred to as CRUD) new databases, tables, or rows in a table. We can do this directly using a database client, or we can have our web application interact with the database. We will see examples of both.