SQL Basics

SQL (Structured Query Language) is the standard language for managing and querying relational databases. It allows you to insert, retrieve, update, and delete data, as well as define database structures.

Core concepts in SQL include:

• Databases & Tables – Data is stored in tables, which are organized into rows (records) and columns (fields).
• Queries – SQL queries let you fetch data using SELECT, filter it with WHERE, and sort it with ORDER BY.
• Inserting & Modifying Data – Use INSERT to add data, UPDATE to change it, and DELETE to remove it.
• Joins – Combine data from multiple tables using INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.
• Aggregations – Use functions like COUNT, SUM, AVG, MIN, and MAX to summarize data.
• Constraints & Keys – Primary keys uniquely identify rows, foreign keys enforce relationships, and other constraints maintain data integrity.
• Indexes – Speed up queries on large tables by creating indexes on frequently searched columns.

SQL works with relational databases such as MySQL, PostgreSQL, SQLite, and SQL Server. It’s a foundation for back-end development, data analysis, and reporting.