How to join your tables using ERD

Why can’t we just have a single table? Navigating relationships in relational databases.

Article written by: Scott A. Adams
Reading: 2 mins.

Scott is a data scientist, social scientist, and educator who cannot think of anything witty to put here.
You are excited to start a new project using data from an unfamiliar relational database. After getting access to the database itself you realize the quality of the documentation is poor — or the documentation is nonexistent. Now you are wondering how to join tables together to create a usable dataset. Sound familiar?
The good news is that it is easy to figure out how to join your tables together using an entity-relationship diagram (ERD), a diagram that shows how tables are related to each other. It is quite simple to generate an ERD using a tool like DbVisualizer. The author uses SQLite database in this article, it can be found here on GitHub.


Normalized relational databases introduce a certain tension between data integrity and usability. Normalization provides protections against messy and inefficient data storage techniques, as well as unintended outcomes resulting from changes to a table. However, obtaining a usable dataset from a normalized database requires work, namely, joins. Fortunately, ERDs can be enormously helpful in understanding how to execute joins in a database, and using DbVisualizer makes the ERD generation process simple.

To read the full article, 9 mins read, please visit Scott A. Adams article Why can’t we just have a single table? navigating relationships in relational databases

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