3 rectangles stacked on top of 1 another.

An introduction to SQL.

Last Tended
Planted
StatusSeed
TagsData, SQL
The letter 'A' in upper and lower case.

Definition

SQL stands for Structured Query Language. Its purpose is to allow users to interact with relational databases. Data is structured in tables. Each table has:

  • 1 column for each field &
  • 1 row for each record.
A table of data.

An SQL statement is composed of:

  • an ordered list of clauses (example: SELECT, FROM, WHERE, …),
  • each clause has its own syntax &
  • each statement ends in ';'.

Example:

/query.sql

SELECT class
FROM fleet;

The above query will return the class column values for all rows in the fleet table.

An elephant's head.

RDBMS

A Relational Database Management System enables a user to define, create, maintain & control access to the database. The system that will accept your SQL query to & return a result. Some of the most common RDBMSs are:

  • Microsoft Azure SQL Database
  • MySQL
  • PostgreSQL (or Postgres)
  • SQLite

Due to its popularity, all examples in this digital garden will be referring to Postgres.

Source

Learning Resources