pátek 23. června 2017

Each database has its own charm, it only takes a while to discover it

Microsoft SQL Server
This is a tough one. But this was the only database that warned me about data corruption when the SSD disk started to fail. While other databases (Oracle, PostgreSQL and MySQL) were silently returning corrupted data. To be fair to other databases, if nothing else, you can [[https://www.postgresql.org/docs/9.5/static/wal-reliability.html|configure]] PostgreSQL to be more resistant to silent errors.

You can relly on the order of the data in the tables, i.e. the tables are not sets, as dictated by relational algebra, but lists! That makes working with the database more intuitive. Of course, some other databases have this property as well (Oracle, MSSQL, SAS) but other not (PostgreSQL, Teradata, Netteza) - generally, all distributed databases use sets.

Another nice property is that you can change the order of the columns in a table any time you want to (in PostgreSQL, for example, you can only append new columns at the end of the tables).

PostgreSQL has the nicest installer on OS X I have ever seen for a database. It's just drag and drop like any other normal app. And after starting the database it tells you the connection parameters. And that's it! No configuration needed! In comparison to an installation of SAS or a full-blooded Oracle, it is Heaven versus Hell. Also, PostgreSQL does not need any configuration fine tuning to be usable. Once, I installed MySQL and PostgreSQL at the same server and mirrored their content. While PostgreSQL worked without any touch for a year, I had to change the configuration of MySQL multiple times, because some default limit (always different one) was too tight.

PostgreSQL, in comparison to MySQL (at least to MariaDB v10), allows renaming of schemas.

Also, PostgreSQL has, in comparison to MySQL, a sane behavior of temporal data types (whenever you are working with timestamps in MySQL, read the documentation - the behavior can be insane, but is documented).

Hand down Oracle has the best execution planner I have ever used. Plus, it provides a rich set of commands.

The best part of SAS's SQL is that it allows you to use some of the data step conventions in the SQL. Do you need to limit the count of the read (not outputted!) rows from a table? No problem, just use inobs parameter! Or is the SQL too inconvenient for your task? Just use SAS code!

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