Next week we see two awesome PostgreSQL conferences in Europe, back to back, with a day in between just so that people may attend both! In chronological order we have first Nordic pgDay in Oslo where I will have the pleasure to talk about Data Modeling, Normalization and Denormalization. Then we have pgday.paris with an awesome schedule and a strong focus on the needs of application developers!
Today I want to react to an article that claims that Relational Algebra Is the Root of SQL Problems in which the author hand-waves the following position:
SQL becomes more a hindrance to data manipulation than an efficient tool. SQL’s greatest problem isn’t in the implementation level, but at its theory foundation. The problem can’t be solved by application optimization. Relational algebra isn’t sophisticated enough for handling the complicated data manipulation scenarios.
Then they go on to several arguments from authority to “prove” their point. My reading of the article is that SQL is very hard when you didn’t care to learn it, as most technologies are.
In this article, we’re going to look at the simple examples provided where apparently SQL makes it so much harder to find a solution compared to writing some Java or C++ code. Contrary to the original article, we go as far as to actually writing both the SQL solution and a complete Python solution, so that we can compare.
In another article here, entitled on JSON and SQL, we saw in great details how to import a data set only available as a giant JSON file. Then we normalized the data set, so as to be able to write SQL and process our data. This approach is sometimes very useful and was a good way to learn some of the JSON functions provided by PostgreSQL.
In this article, we’re going to use SQL to export the data from our relational model into a JSON document. The trick that makes it complex in this example is that we have a recursive data model, with a notion of a parent row that exists in the same table as the current one. That’s a nice excuse to learn more about the SQL construct WITH RECURSIVE.
It seems to be usual nowadays to review the previous year, and readers apparently like Top-N Lists — that’s you now, so let’s hope that my understanding works with you too.
Of course 2018 will see its own amount of new and original content added to this blog, with a continuous focus towards how to make the best out of the SQL powerful programming language, and its advanced concurrency semantics.
PostgreSQL ships with an interactive console with the command line tool named psql. It can be used both for scripting and interactive usage and is moreover quite a powerful tool. Interactive features includes autocompletion, readline support (history searches, modern keyboard movements, etc), input and output redirection, formatted output, and more.
