Let me give you an overview of the programming languages you'll need as a data engineer. Let's start with the most basic ones -

SQL

Every programmer needs to know SQL. The Structured Query Language lets your interact with relational databases, ingress and egress data easily. SQL is very easy to learn and one can get started with basic commands easily.

If you wish to make a career as data engineer, SQL is your best friend.

Python

Python is another must to make an entry into data engineering. Python is very popular among data engineers and data scientists equally. It's open-source and has a vast community to support you during your learning.

You can ask questions and get answers quickly.

There are several libraries that are specifically meant for data-science side of the things like NumPy, Pandas, Keras etc. For data engineering, you'll do well even if you know the basics of Python.

For beginning a career in data engineering, you will do well even if you know only SQL and Python. Following few languages may help if you wish to explore data-science along with data engineering.

R Programming Language

R is a robust, open-source programming language that's gaining popularity among data engineers. It's got a growing community and a lot of enthusiasts who're eager to help with common R questions and data engineering concepts.

Java

You can't go wrong with Java. It's one of the most popular languages and is being used in several data engineering projects globally by large enterprises. If you know Java, picking up Python and other programming languages should be a cakewalk for you.

Scala

Scala has its own fanbase in the world of data engineering. It's gaining popularity and is one of the top languages if you look for big data technologies. The community support is growing; but still limited as compared to other programming languages.

Which data engineering programming language is easiest to learn?

I'd say Python. It's got a very expressive syntax which is easy to grasp. There are plenty of code snippets available on Github repos which you can use to understand basic programming concepts.

I hope that answers your question. Feel free to ask and I'll try my best to answer.