PostgreSQL - What is SQL
Course Syllabus
What is SQL?
SQL (Structured Query Language) is the universal computer language designed to store, retrieve, filter, and transform structured data inside Relational Database Management Systems (RDBMS). If you have ever organized information in an Excel spreadsheet or Google Sheet, you already understand the core structure of a database: tables made of rows and columns.
Relational Databases vs. Spreadsheets & Raw Files
While spreadsheets work well for small personal data sets, production web applications, banking systems, and e-commerce platforms process millions of concurrent transactions per second. Relational databases like PostgreSQL, MySQL, and SQLite provide strict data integrity guarantees, concurrent access control, indexing for lightning-fast lookups, and standardized SQL query capabilities.
- Tables (Entities): Collections of related records (e.g.
vehicles,users,orders). - Columns (Attributes): Fields defining specific properties and data types (e.g.
make_modelas text,wheelsas integer). - Rows (Records): Individual data instances (e.g. a single vehicle record).
- Primary Key (PK): A unique column (like
id) ensuring every row can be uniquely identified without ambiguity.
Writing Your First SQL Query
SELECT * FROM vehicles;
The asterisk (*) acts as a wildcard instructing SQL to return all available columns from the specified table.
🚗 Table: Vehicles
🗄️ Schema Explorer SELECTABLE
🎯 Exercises Checklist:
💡 Hint:
Loading hint...
🔑 Solution SQL:
SELECT * FROM movies;Data Output
No results. Run query to fetch data.