Query Life Cycle

Both data engineers and data users write queries every day, but not everyone is familiar with how query works internally. While we trust the database engine to do all the magic and return us the expected result, it's still worth understanding what goes on behind the scenes, and the knowledge can further help us enhance query performance.

Imperative language vs. declarative language

There are two programming paradigms: imperative and declarative. The most commonly used programming languages, like Python and Java, are imperative. They instruct the computer on how the code should run by giving a sequence of steps.

For example, we want to find an item from a list, and the Python implementation can look like the following. The program loops over the dictionary and compares each item with the target. With imperative languages, we have full control over the implementation.