Introduction to SQL

After we introduced the most popular conceptual Data Model, Entity-Relationship (ER), and the most popular logic data model (the Relational Model), it’s time to introduce SQL.

SQL (Structured Query Language) is a language we use to interact with a Database Management System (DBMS).

As the name suggests, it’s not a programming language, but it was born as a querying language, and later evolved to an interface to doing more advanced operations with a database than just performing queries.

I said “evolved”, but in reality SQL is always evolving. It’s a standard that was first published in 1986, then updated in 1989, 1992, 1999, 2003, 2006, 2008, 2011, 2016, 2019, and as its latest published edition, SQL:2023 (ISO/IEC 9075:2023).

SQL is implemented in many popular DBMS: PostgreSQL, MySQL, Oracle, SQLite, MicroSoft SQL Server, and many more. Each different database implements the standard, or a particular version of it, and adds custom features on top of it, to simplify creating queries or adding a specific functionality.

Unless noted otherwise, every time I talk about SQL I talk about the SQL standard, not a particular implementation of it.

If you’re writing SQL and it gets messy, I built a free SQL formatter that prettifies your queries in the browser.

SQL is a huge subject. I cover many of its topics in different blog posts, including:

SQL, creating a table SQL, adding data to a table SQL, how to use SELECT SQL, how to update a table structure SQL, how to update data SQL, how to delete data and tables SQL, Handling empty cells SQL, Unique and Primary keys SQL Views SQL Joins

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