AL2Meta

SQL

SQL stands for Structured Query Language.

SQL is a standard language used to communicate with relational databases—to store, retrieve, update, and manage data.

In simple terms:
👉 SQL is how you talk to databases like MySQL, MariaDB, PostgreSQL, and SQL Server.

What SQL is used for

  • Creating databases and tables
  • Inserting new data
  • Reading (querying) data
  • Updating existing records
  • Deleting records
  • Managing users and permissions

Basic SQL example

SELECT name, email
FROM users
WHERE active = 1;

This means:
➡️ “Get the names and emails of all active users.”

Core SQL operations (CRUD)

  • CREATE – make tables/databases
  • READ – query data (SELECT)
  • UPDATE – change data (UPDATE)
  • DELETE – remove data (DELETE)

Key SQL concepts

  • Tables → rows & columns
  • Primary key → unique row identifier
  • Foreign key → links tables together
  • Indexes → speed up searches
  • Joins → combine data from multiple tables

SQL vs databases

Important distinction:

  • SQL = the language
  • MySQL / MariaDB / PostgreSQL = database systems that use SQL

Think of it like:

  • English = SQL
  • Different people = MySQL, MariaDB, PostgreSQL (all speak English with accents)

SQL in web development

Typical flow:

  1. User submits a form
  2. Backend code (PHP, Python, Node.js) runs SQL
  3. Database returns results
  4. Webpage displays data

Variants

Each database adds small differences:

  • MySQL / MariaDB → MySQL-style SQL
  • PostgreSQL → more strict, feature-rich SQL
  • SQL Server → T-SQL

But core SQL is universal.

Leave a Reply