@@ -153,37 +153,91 @@ provider.
   and data connections on top of Amazon Web Services instances.
 
 
-## General database resources
-* [How does a relational database work?](http://coding-geek.com/how-databases-work/)
-  is a detailed longform post on the sorting, searching, merging and other
-  operations we often take for granted when using an established relational 
-  database such as PostgreSQL.
+### SQL resources
+You may plan to use an 
+[object-relational mapper (ORM)](/object-relational-mappers-orms.html)
+as your main way of interacting with a database, but you should still
+learn the basics of SQL to create schemas and understand the SQL code
+generated by the ORM. The following resources can help you get up to
+speed on SQL if you have never previously used it.
 
 * [Select Star SQL](https://selectstarsql.com/) is an interactive book for
   learning SQL. Highly recommended even if you feel you will only be working
   with an [object-relational mapper](/object-relational-mappers-orms.html)
   on your projects because you never know when you will need to drop into
   SQL to improve a generated query's slow performance.
 
-* [Why I Love Databases](https://medium.com/@jeeyoungk/why-i-love-databases-1d4cc433685f)
-  is a great read on the CAP Theorem, distributed systems and other topics
-  that are at the core of database theory and implementation. Well worth
-  the time to read.
+* [A beginners guide to SQL](https://www.sohamkamani.com/blog/2016/07/07/a-beginners-guide-to-sql/)
+  does a good job explaining the main keywords used in SQL statements
+  such as `SELECT`, `WHERE`, `FROM`, `UPDATE` and `DELETE`.
+
+* [SQL Tutorial](https://sqlzoo.net/) teaches the SQL basics that can be 
+  used in all major relational database implementations.
+
+* [Life of a SQL query](https://numeracy.co/blog/life-of-a-sql-query)
+  explains what happens both conceptually and technically within a
+  database when a SQL query is run. The author uses 
+  [PostgreSQL](/postgresql.html) as the example database and SQL syntax
+  throughout the post.
+
+* [A Probably Incomplete, Comprehensive Guide to the Many Different Ways to JOIN Tables in SQL](https://blog.jooq.org/2017/01/12/a-probably-incomplete-comprehensive-guide-to-the-many-different-ways-to-join-tables-in-sql/)
+  elaborates on one of the trickiest parts of writing SQL statements
+  that bridge one or more tables: the `JOIN`.
 
 * [Writing better SQL](http://www.craigkerstiens.com/2016/01/08/writing-better-sql/)
   is a short code styling guide to make your queries easier to read.
 
-* [A one size fits all database doesn't fit anyone](https://www.allthingsdistributed.com/2018/06/purpose-built-databases-in-aws.html)
-  explains Amazon Web Services' specific rationale for having so many types 
-  of relational and non-relational databases on its platform but the article
-  is also a good overview of various database models and their use cases.
+* [SQL Intermediate](https://www.dataquest.io/blog/sql-intermediate/) is a
+  beyond-the-basics tutorial that uses open data from the 
+  [US Consumer Financial Protection Bureau](https://www.consumerfinance.gov/)
+  as examples for counting, querying and using views in PostgreSQL. 
+
+
+### General database resources
+* [How does a relational database work?](http://coding-geek.com/how-databases-work/)
+  is a detailed longform post on the sorting, searching, merging and other
+  operations we often take for granted when using an established relational 
+  database such as PostgreSQL.
+
+* [Databases 101](https://thomaslarock.com/2018/07/databases-101/) gives a
+  great overview of the main relational database concepts that is relevant
+  to even non-developers as an introduction.
+
+* [Five Mistakes Beginners Make When Working With Databases](http://www.craigkerstiens.com/2016/06/07/five-mistakes-databases/)
+  explains why you should not store images in databases as well as why to be 
+  cautious with how you normalize your schema.
 
 * [DB-Engines](http://db-engines.com/en/ranking) ranks the most popular
   database management systems.
 
 * [DB Weekly](http://dbweekly.com/) is a weekly roundup of general database 
   articles and resources.
 
+* [Online migrations at scale](https://stripe.com/blog/online-migrations)
+  is a great read on breaking down the complexity of a database schema
+  migration for an operational database. The approach the author's team
+  used was a 4-step dual writing pattern to carefully evolved the way
+  data for subscriptions were stored so they could move to a new, more
+  efficient storage model.
+
+* [A one size fits all database doesn't fit anyone](https://www.allthingsdistributed.com/2018/06/purpose-built-databases-in-aws.html)
+  explains Amazon Web Services' specific rationale for having so many types 
+  of relational and non-relational databases on its platform but the article
+  is also a good overview of various database models and their use cases.
+
+* [SQL is 43 years old - here’s 8 reasons we still use it today](https://blog.sqlizer.io/posts/sql-43/)
+  lists why SQL is commonly used by almost all developers even as the
+  language approaches its fiftieth anniversary.
+
+* [SQL keys in depth](https://begriffs.com/posts/2018-01-01-sql-keys-in-depth.html)
+  provides a great explanation for what primary keys are and how you 
+  should use them.
+
+* [Exploring a data set in SQL](https://tapoueh.org/blog/2017/06/exploring-a-data-set-in-sql/)
+  is a good example of how SQL alone can be used for 
+  [data analysis](/data-analysis.html). This tutorial uses Spotify data
+  to show how to extract what you are looking to learn from a data set.
+
 * [Databases integration testing strategies](https://julien.danjou.info/blog/2014/db-integration-testing-strategies-python)
   covers a difficult topic that comes up on every real world project.
 
 
@@ -25,7 +25,7 @@ statements or stored procedures.
 
 For example, without an ORM a developer would write the following SQL
 statement to retrieve every row in the USERS table where the
-``zip_code`` column is 94107:
+`zip_code` column is 94107:
 
     SELECT * FROM USERS WHERE zip_code=94107;
 
 
@@ -79,6 +79,11 @@ security controls so make sure to lock down your instances.
   each of the items on the 
   [official MongoDB security checklist](https://docs.mongodb.com/manual/administration/security-checklist/).
 
+* [The definitive guide to MongoDB security](https://opensource.com/article/19/1/mongodb-security)
+  is a high-level overview for the multitude of tasks you must perform
+  to lock down your MongoDB instances, such as appropriately using SSL 
+  certificates and access-control lists.
+
 * [MongoDB Security Basics For Your Deployments in AWS](https://www.mongodb.com/blog/post/mongodb-security-basics-for-your-deployments-in)
   is primarily a guide on AWS security from the perspective of using 
   installing and using MongoDB on your own instance. The post covers 
 
@@ -98,6 +98,19 @@ which is defined by the
   and then relates JavaScript evolution since the mid-90s to explain the
   history of the problem.
 
+* [How JavaScript works: the rendering engine and tips to optimize its performance](https://blog.sessionstack.com/how-javascript-works-the-rendering-engine-and-tips-to-optimize-its-performance-7b95553baeda)
+  is one particularly relevant post in a multi-part series that explains
+  how you can optimize slower JavaScript code to better suit the JS engines
+  in common web browsers.
+
+* [How to reduce the impact of JavaScript on your page load time](https://engineering.gosquared.com/improve-javascript-page-load-time)
+  provides insight into minimizing the size and improving the download
+  and execution speed for JavaScript libraries, especially ones that are
+  used at scale by many websites.
+
+* [Learn JS data](http://learnjsdata.com/) teaches how to manipulate data
+  using JavaScript in a browser or on the server using Node.js. 
+
 
 ### JavaScript learning checklist
 1. Create a simple HTML file with basic elements in it. Use the
 
@@ -52,6 +52,11 @@ ease further development and deployment. This approach is called the
   provides some advice on using microservices in a fairly early stage of
   a software project's lifecycle.
 
+* [Why Microservices?](https://dev.otto.de/2016/03/20/why-microservices/)
+  presents advantages microservices can bring to an existing monolithic
+  application where it is clear what needs to be broken down into smaller
+  components to make it easier to iterate and maintain.
+
 * [Developing a RESTful microservice in Python](http://www.skybert.net/python/developing-a-restful-micro-service-in-python/)
   is a good story of how an aging Java project was replaced with a
   microservice built with Python and Flask.
@@ -89,3 +94,8 @@ ease further development and deployment. This approach is called the
 
 * In the [Microservices with Docker, Flask, and React](http://testdriven.io/) course, you will learn how to quickly spin up a reproducible development environment with Docker to manage a number of microservices. Once the app is up and running locally, you'll learn how to deploy it to an Amazon EC2 instance. Finally, we'll look at scaling the services on Amazon EC2 Container Service (ECS).
 
+* Zuul is open source proxy for combining multiple microservices into a 
+  unified API call. Check out this post on 
+  [Using Netflix Zuul to Proxy your Microservices](https://blog.heroku.com/using_netflix_zuul_to_proxy_your_microservices)
+  to learn more and get started using it.
+
@@ -51,6 +51,15 @@ A cache can be created for multiple layers of the stack.
   [downsides to caching](https://msol.io/blog/tech/2015/09/05/youre-probably-wrong-about-caching/)
   that many developers fail to take into consideration.
 
+* [Caching at Reddit](https://redditblog.com/2017/1/17/caching-at-reddit/)
+  covers monitoring, tuning and scaling for the very high scale 
+  [Reddit.com](https://www.reddit.com/) website.
+
+* [Mastering HTTP caching](https://blog.fortrabbit.com/mastering-http-caching)
+  provides more advanced advice on caching dynamic as well as static 
+  content via CDNs and other configurations.
+
+
 
 ## Caching learning checklist
 1. Analyze your web application for the slowest parts. It's likely there are
 
@@ -140,6 +140,10 @@ certain threshold.
   shows how to log errors more accurately to pinpoint the problem instead of
   receiving generic exceptions in your logs.
 
+* [Python and Django logging in plain English](https://djangodeconstructed.com/2018/12/18/django-and-python-logging-in-plain-english/)
+  is a wonderful overview of how to configure logging in 
+  [Django](/django.html) projects.
+
 
 ## Logging learning checklist
 1. Read how to integrate logging into your web application framework. 
 
@@ -15,7 +15,13 @@ on GitHub.
 
 
 ## 2019
+### February
+* Refreshed the [relational databases](/databases.html) page with new 
+  resources and removed some out-of-date ones.
+
 ### January
+* Merged [PR #202](https://github.com/mattmakai/fullstackpython.com/pull/202)
+  to fix a typo on the [web frameworks](/web-frameworks.html) page.
 * Updated the [source control](/source-control.html) page with more 
   resources.
 * Added new post on the