Practical SQL Guide: Building and Querying a School Database with PostgreSQL

A data analyst demonstrates how to design and query a relational database for a fictional institution called Greenwood Academy using PostgreSQL. The project covers three core SQL language categories: Data Definition Language (DDL) for creating and modifying table structures, Data Manipulation Language (DML) for inserting and updating records, and Data Query Language (DQL) for retrieving data. Three tables — students, subjects, and exam_results — were created within a dedicated schema to keep the database organized. The guide also highlights best practices such as prefixing table names with the schema name to avoid misdirected table creation. Additional topics covered include filtering results, using specialized operators, and writing conditional logic with CASE WHEN statements.