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SQL

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An introduction to SQL.

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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.

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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
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