It seems you are missing a few tags... What you will find in software dev- is that things are often organized into toolchains, and you can mix'n match. For instance if you know python, you're going to pretty much work on a lot of OS/script specific stuff, you'll probably also know C, and C++. I am not sure what else a python dev will know, it is not as familiar to me.
If you know .NET, you'll probably work with either C#, or VB, possibly both. You'll learn SQL for sure, because that's the defacto for interfacing and querying with the database. There are a few options for databases, MySQL, Oracle, SQL Server (Microsoft) etc. Typically C#, and VB developers work with SQL Server, but I have seen VB jobs which use Oracle. The Database was originally the solution for enterprise islands of information. When you have more than one DB things tend to get messy, so if you ever have the option don't mix'n match the databases.
So essentially what you need to know is that when you develop, you can't really choose only one language to develop in, you're developing infrastructure. Infrastructure requires quite a few tools to do your job effectively. I do have a favorite language, although that's sometimes a liability. My favorite is C#. I am equally good at Java.
**My toolchain will probably look like this; C# .NET, JS, CSS, HTML, ASP.NET, SQL (Specifically MS SQL Server). **
//danni there appears to be a problem with the bolding, previous sentance.
Java developers typically use Oracle or MySql for databases. Everybody needs web development tools like JS, HTML, and CSS. I am assuming that most of us are web developers these days. Apparently if you're only developing shell tools you'll have a more OS specific tool chain.