I am designing a mySQL database. I created tables and added extra columns for future use. Will it affect performance?
--LinkedIn.com

Why you should never, ever, ever use MongoDB

Fixing 7 common database design errors

Amazon's MySQL database challenger Aurora exits preview

The First Normal Form in Theory and Practice, Part I

• New Appendix to paper #3: While working on my book, I collected all comments by readers and replies by me (edited) and David McGoveran and added them as Appendix B. It further clarifies some of the aspects of the proposed relational/2VL solution to missing data. Those who ordered the paper in 2014 and 2015 should email me for a copy.

• Added to LINKS page: 

Why even the most intelligent software architects don't understand the Relational Model

In 15-20 years from now: Information will stay only in XML (no more tuples, no more objects). Imperative languages as we know them today (Java, C, C++, C#) will be gone. We will program with some extension of XQuery, or in any case a declarative dataflow/workflow language specially --Daniela Florescu, 2010 Interview

Exactly 20 years ago I wrote this article: "Storing and Querying XML Data using an RDMBS". I curse myself every day for doing so. I should be damned by the fires of hell for ever opening my mouth and letting people believe that one can REASONABLY use SQL to query hierarchical, complex structures like XML or JSON.  NO, PEOPLE. YOU CAN NOT! --Daniela Florescu, 2015, LinkedIn.com

SQL Will Inevitably Come To NoSQL Databases

Data Scientists: The talent crunch (that isn't)

• What ORMs have taught me: just learn SQL
• What’s left of NoSQL?
• Complicating a metaphor
• Data Scientists are bullies that need a guiding hand

Read it all. (Please comment there, not here)

"... web apps ushered in a new model for development and distributed systems that ... [r]elational databases are fundamentally ill suited to handle ... Their master-slave architectures, methods for writing and reading data, and data distribution mechanisms simply cannot meet the key requirements of modern web, mobile and IoT applications. I tell you that not as an employee of a NoSQL company, but as a guy who has worked with RDBMS’s for over twenty-five years. In short, you simply can’t get there from here where relational technology is concerned, and that’s why NoSQL must be used for the applications we’re talking about.

My feeling is that the field of NoSQL was created EXACTLY so the data should not be normalized like in relational databases--which has the disadvantages that data needed for real time/online applications needed to be joined at runtime before being used by the application. Under the time constraints of an online system, this is unacceptable. Hence, application developers want to store persistently the data EXACTLY in the way application see it: pre-aggregated, potentially inconsistent, and potentially replicated. Bottom line, there is no "rule" of how you should store the data. Just look at your application needs. Not everyone has the same requirements as iTunes or Netflix, so you don't need to copy their design.
...
If this is a question for you... maybe you shouldn't be using a NoSQL database in the first place !? Why do you think you need one and good old relational databases aren't good for you? Just because it's "fashionable" ? My point is: if you knew exactly WHY you need a NoSQL database, you knew EXACTLY how to structure your data for it.
--LinkedIn.com

Data Modeling in NoSQL

• Something Does not Make Sense  
• Help us define data scientist for a kid

• What's the Harm In a Default Setting For Div By Zero  
• Enterprise financials in the cloud: Why the fog of skepticism may be lifting

• Extending the relational algebra to capture less meaning (h/t Erwin Smout)
• Thinking for Programmers (h/t William Sisson)